Preheat the oven to 350°F. Butter a 9-inch springform pan and line the bottom with parchment paper. In a bowl, using an electric mixer, beat together the butter, sugar, and lemon zest until light and fluffy, 3 to 5 minutes. Add the egg yolks, beating to combine. Mix in the ricotta and vanilla. Add the flour, baking powder, and salt. Beat until smooth, then stream in the milk. Mix until combined. In a bowl, using an electric mixer, whisk the egg whites until stiff peaks form, 3 to 5 minutes. Gently mix the whites into the batter until the batter is smooth with no streaks. Toss the blueberries with 1 tablespoon flour. Mix the berries into the batter. Scrape the batter into the prepared pan. Swirl in the blueberry jam, leaving streaks of jam throughout the batter. Bake 50-60 minutes, tenting with foil at 30 minutes. The longer you bake, the more set your cake will become. I bake mine for 55 minutes. To make the glaze. In a bowl or glass measuring cup, whisk together all ingredients. The glaze will be thin. Pour the glaze over the cake. Serve warm with whipped cream or ice cream.: As the oven warms, you should notice a faint electrical hum and the heat slowly becoming steady, which helps the cake rise evenly. Make sure the rack is in the center so the top browns without overcooking the edges. A common error is placing the pan too close to the top heating element, which leads to uneven browning. If your oven runs hot, consider setting it a few degrees lower and using an oven thermometer for accuracy. Proper preheating ensures the leavening activates immediately, giving the batter lift rather than a slow, uneven rise.
Butter a 9-inch springform pan and line the bottom with parchment paper: Greasing the pan and lining the bottom with parchment creates a smooth release and prevents sticking, while the edges can brown against the metal for texture contrast. Press the parchment into the base so it lays flat. Failing to properly grease the sides can cause the cake to tear when releasing. Butter also contributes subtle flavor to the crust, so don't skip it even with parchment in place.
Beat together the butter, sugar, and lemon zest until light and fluffy, 3 to 5 minutes: During this creaming stage you will hear a quieter, aerating sound from the mixer and see the mixture turn paler and fluffier as air is incorporated. This trapped air helps form the cake's structure. Scrape down the bowl periodically to ensure even mixing. Overmixing at high speed can warm the butter too much, making the batter heavy. Aim for a light, billowy texture that holds soft peaks when shifted.
Add the egg yolks, beating to combine: After adding the yolks, the batter will feel silkier and take on more volume, while the color deepens slightly. Incorporating yolks slowly keeps the mixture emulsified, preventing separation. If you add yolks too quickly, the batter can curdle, creating a grainy texture. Mixing until homogenous ensures the fat disperses and binds with the creamed butter and sugar .
Mix in the ricotta and vanilla: When you add the ricotta , the batter becomes creamier, and you'll notice a gentle, milky aroma. The ricotta gives the cake its pudding like interior, contributing tenderness and tang. If the ricotta is too watery, drain it briefly on a towel to avoid thinning the batter. Stir just until the mixture is smooth and glossy to keep the emulsion intact.
Add the flour, baking powder, and salt: As the dry ingredients are incorporated, the batter will thicken and take on a dough like quality before liquids are added. Use a gentle folding motion to combine to avoid activating gluten excessively, which would toughen the cake. Overworking here is a common mistake, leading to a denser crumb. Sifting the flour and baking powder beforehand can help a uniform texture and even rise.
Beat until smooth, then stream in the milk: The batter should become smooth and cohesive; streaming in the room temperature milk helps loosen it without shocking the emulsion. You will notice a glossy sheen as the liquid integrates. Adding cold liquid or too quickly can deflate incorporated air. Aim for a pourable consistency that still holds some body, since the whipped egg whites will lighten it further.
Whisk the egg whites until stiff peaks form, 3 to 5 minutes: As you whisk, the mixture will change from glossy to cloudlike, and you will hear a higher pitched, airy rhythm from the mixer. Stiff peaks mean the whites hold firm points when lifted but are still moist. Underwhipping makes the final cake dense, while overwhipping can cause dryness and difficulty folding. Stop when peaks hold shape but still look satiny.
Gently mix the whites into the batter until the batter is smooth with no streaks: After folding in the whipped egg whites , the batter should feel light and airy, with no visible white streaks. Use a gentle scooping and turning motion to preserve the air. A mistake here is aggressive stirring, which knocks out the aeration and yields a heavier cake. The result should be a homogeneous, slightly billowy batter that ripples softly as you move the spatula.
Toss the blueberries with 1 tablespoon flour: Coating the blueberries keeps them suspended and prevents them from sinking while baking. You will see the berries take on a dusting that absorbs surface moisture. If you skip this step, fruit can settle and create dense pockets. For frozen blueberries , toss them straight from the freezer to minimize bleeding into the batter.
Mix the berries into the batter: When you fold in the dusted blueberries , you will spot vibrant dots of color and occasional juice streaks where the fruit rubs against the batter. Gentle folding distributes fruit without crushing the berries. Overmixing will burst too many berries, making the batter purple and wetter. Aim for even distribution so each slice has balanced fruit.
Scrape the batter into the prepared pan: The batter should slide out in a thick ribbon, filling the pan evenly. Use a spatula to smooth the top so it bakes uniformly. Leaving uneven high spots can cause irregular rising and browning. Tapping the pan gently on the counter removes large air pockets for a consistent crumb.
Swirl in the blueberry jam: As you dollop and drag blueberry jam through the batter, you will see glossy ribbons that promise concentrated bursts of flavor after baking. The jam both flavors and creates visual interest. Too much jam can create soggy pockets, so aim for streaks rather than large pools. The jam will caramelize slightly on the surface, adding depth to each bite.
Bake 50 to 60 minutes, tenting with foil at 30 minutes: During baking the kitchen will fill with lemon and baked blueberry aromas, and the top should gently brown. Tenting with foil at the halfway mark prevents overbrowning while allowing the interior to continue setting. If you underbake, the center may wobble and be too soft, while overbaking will create a drier texture. I usually aim for about 55 minutes, checking for a slight jiggle in the center that signals a custardy finish.
To make the glaze, whisk together all ingredients: The glaze will be thin and pourable, shining as it comes together. Pouring it over the warm cake allows it to soak in and add brightness from the lemon juice and sweetness from the powdered sugar . If the glaze is too thick, add a little more lemon juice , and if too thin, add a touch more powdered sugar . A lumpy glaze can be smoothed by whisking vigorously or straining.
Pour the glaze over the cake and serve warm with whipped cream or ice cream: As the glaze settles, it gives the surface a glossy finish and a tangy kiss of citrus. Serving warm enhances the jam pockets and the custard like center, and a scoop of whipped cream adds cool contrast. Avoid serving it too hot, which can make the texture feel runny, or too cold, which mutes the aroma. A warm slice with a spoonful of cream is how I enjoy it most.