Preheat the oven to 350 degrees. Spray a 9 x 5 inch loaf pan with nonstick spray. In a bowl, whisk together the flour, baking powder and salt.: You will smell the initial warmth in the kitchen as the oven comes up to temperature, and the consistent heat ensures even rise and browning. I set my oven early so the interior reaches a stable heat, which prevents the cake from baking unevenly. If the oven is not fully preheated the cake can bake too slowly and collapse in the center, so wait until it reaches a steady 350 degrees. A common mistake is setting the pan in too soon, which can cause underbaked spots. Keep your loaf pan ready and check the oven gauge if needed.
In the bowl of an electric mixer, beat the butter and sugar until light and fluffy, about 5 minutes. Beat in the eggs 1 at a time. Beat in the ricotta cheese, lemon juice and vanilla extract until combined.: The faint scent of oil will be noticeable as you spray, and a well prepared pan ensures the cake releases cleanly. I sometimes line the pan with parchment along the bottom to make lifting easier, but a light spray alone usually does the trick. If you skip proper greasing, the crust can stick and tear when you invert the loaf. A troubleshooting tip is to run a knife gently along the edge after cooling if release seems hesitant.
With the mixer on low speed, beat in the dry ingredients until they are just combined. Do not overmix!: As you whisk, notice the powdery, slightly toasted aroma of the dry mix coming together. This step distributes the leavener and salt evenly so every bite rises and tastes balanced. Sifting is optional, but whisking breaks up clumps and aerates the mixture. A common error is adding the leavening unevenly, which creates pockets of odd texture in the crumb, so take a moment to mix thoroughly.
Toss the blueberries with the 1 tablespoon of flour. Add the blueberries to the batter and use a spatula to fold them in.: You will hear a steady whir as the butter and sugar aerate, and the mixture will lighten in color and texture. This aeration traps tiny air bubbles that help create a tender crumb. If the butter is too cold the mixture will stay lumpy, and if it is too warm it may look greasy. Beat for the time specified until it becomes pale and fluffy to ensure proper structure.
Spread the batter in the loaf pan. Bake the cake for 55 to 60 minutes, or until a tester inserted in the center comes out clean. Remove the cake from the oven and let it cool for 20 to 30 minutes before inverting it onto a dish, cooling rack or parchment paper. Let it cool completely before glazing.: Each egg will incorporate with a slight change in texture, and adding them separately helps the batter emulsify smoothly. The sound will shift as the mixer works the mixture into a glossy batter. If you add all the eggs at once you risk a broken emulsion, which can make the batter split. A sign of trouble is a curdled looking batter; if that happens, beat in a spoonful of flour to help bring it back together.
To make the lavender glaze, whisk all ingredients together until smooth. If it seems too thick, add in more milk 1 teaspoon at a time. If desired, you can add a drop of food coloring to make it pinkish-purple!: The batter will take on a creamier feel as the ricotta cheese blends in, and you will notice a fresh citrus lift from the lemon juice . This addition keeps the crumb moist and adds subtle tang. Over mixing here can break down the texture, so stop as soon as the ingredients are evenly distributed. If you see visible lumps of ricotta cheese , gently mix until smooth without vigorous beating.
Once the glaze is smooth, drizzle it over the cake. Let it sit until it firms up before slicing.: At this stage the sound softens and the batter becomes smoother; you want to stop when streaks disappear. Gentle mixing prevents developing too much gluten from the all purpose flour , which would make the cake tough. A typical mistake is over mixing, which yields a tighter crumb. If you notice a glossy, elastic texture forming, you have likely overworked the batter and might end up with a denser loaf.
Optional: sprinkle a teaspoon of culinary lavender over top of the glaze.: The batter should be uniform but not beaten to stretch the gluten, and you will see a soft thick consistency that still moves slowly when the bowl is tapped. The touch test is helpful; the batter should hold its shape but spread slightly. Overmixed batter can produce a chewy texture instead of the desired tender crumb. If this happens, resist the urge to keep mixing and proceed to the next step.
Toss the blueberries with the 1 tablespoon of flour: The blueberries will pick up a light dusting that helps them stay suspended in the batter, and you can see them become slightly matte rather than glossy. This small trick prevents them from sinking to the bottom during baking. If you skip this, the fruit often collapses down and leaves a dense fruit layer. Be careful not to overcoat, a light toss is sufficient.
Add the blueberries to the batter and use a spatula to fold them in: Folding creates minimal disturbance while distributing the fruit, and you will notice bluish streaks appearing in the batter as you work. Use a slow turn and scrape motion to avoid bursting the blueberries and coloring the batter too much. If you fold too vigorously the fruit will burst and the color will bleed, altering the cake appearance and texture. Fold until the fruit is just evenly spread.
Spread the batter in the loaf pan: The batter will feel thick and slightly lumpy from the fruit, and as you smooth the top you can see where it will form a gentle dome. Tapping the pan on the counter once will settle air pockets. A mistake here is over smoothing which can compress the batter; gentle evening is best. Ensure the batter reaches near the top without spilling over for an even bake.
Bake the cake for 55 to 60 minutes, or until a tester inserted in the center comes out clean: The aroma of baked butter and fruit will fill your kitchen as the top turns a light golden shade, and you will hear the faint pulling sound as the cake sets. The tester coming out clean is the clearest signal of doneness; if it comes out with wet batter continue baking in small increments. Removing the cake too early will leave a raw center, while leaving it too long can dry the crumb.
Remove the cake from the oven and let it cool for 20 to 30 minutes before inverting it onto a dish, cooling rack or parchment paper: Cooling allows the crumb to set and prevents tearing when unmolding, and the warmth will become a comforting, baked aroma that drifts through the kitchen. If you try to remove it while piping hot it can collapse or stick. Patience here results in a clean release and intact loaf.
Let it cool completely before glazing: The cake will firm as it cools and the crumb will stop releasing steam, ensuring the glaze sits on the surface rather than melting away. If you glaze a warm cake the icing will run off and become thin. A good sign it is ready is when the loaf feels room temperature to the touch.
To make the lavender glaze, whisk all ingredients together until smooth: You will see the powdered sugar dissolve into the cream and milk , forming a glossy mixture. The aroma of lavender extract will be gentle and floral, and the texture should be pourable. If the glaze seems too thick, add more milk 1 teaspoon at a time until it reaches a drizzling consistency. Over thinning will make the glaze runny and translucent, so add liquids slowly.
If it seems too thick, add in more milk 1 teaspoon at a time: Each small addition changes the body of the glaze noticeably, and you will see it shift from a stiff paste to a flowing ribbon. Test the flow by lifting the whisk; it should form a slow ribbon that disappears into the surface. Adding too much liquid quickly will make the glaze too thin to set properly.
If desired, you can add a drop of food coloring to make it pinkish purple: A single drop will tint the glaze lightly and make the loaf feel festive, and the visual contrast against the golden top is pleasing. Too much coloring can look artificial, so proceed sparingly. Mix thoroughly to ensure an even hue.
Once the glaze is smooth, drizzle it over the cake: The glaze should flow in a glossy ribbon, settling into gentle waves as it cools. Use a spoon or piping motion to control the coverage, and stop when you have a pleasing sheen. If the glaze sets too quickly while you are working, warm it briefly to regain fluidity. Uneven glazing can be remedied by letting it firm and adding a second, lighter drizzle.
Let it sit until it firms up before slicing: The glaze will form a thin shell and the aroma of lavender extract will linger; waiting ensures neat slices and a pleasant mouthfeel. Cutting too soon will smear the glaze and make slices messy. Patience yields tidy, attractive portions.
Optional: sprinkle a teaspoon of culinary lavender over top of the glaze : The small floral crunch of dried culinary lavender flowers adds a pretty finishing touch and an extra hint of fragrance. Use only a light sprinkle, as too much can taste soapy. If you are uncertain, try a tiny pinch first to judge the strength.