Preheat oven to 350 degrees. Spray a 9 x 13” pan with cooking spray.: The room will start to warm as the oven comes up to 350 degrees , and that gentle heat primes the pan so the batter begins cooking the moment it hits the metal. You want a well oiled pan so the cake releases cleanly, which preserves the pretty top where the candies will sit. A common slip is under greasing, which makes the cake cling to the pan and tear when removed, so be generous with spray or a light layer of butter.
Whisk together flour, baking powder, and salt in a medium bowl. Set aside.: When you whisk the dry flour with the baking powder and salt , you are aerating and evenly distributing the leavening so the cake rises uniformly. The texture should look powdery and even, with no lumps of baking powder. If you skip this step or mix poorly, you risk uneven pockets of lift or a flat cake, so take a moment to combine well.
Stir eggs, melted butter, sugar, and vanilla in a large bowl. Add half the milk and half the flour mixture, stir until just combined. Add the remaining milk and flour mixture and stir until the dough just comes together, scraping the bowl as necessary.: The batter will feel slightly thick but pourable, with a glossy sheen from the melted butter . When you add the dry and wet components in two parts, you reduce over mixing, which keeps the crumb tender. Listen for the soft slap of the spatula on the bowl and notice how the batter ribbons slowly back when lifted. Overworking here will develop gluten and make the cake dense, so stop mixing once you see no streaks of flour.
Pour half the batter into the prepared pan and spread to cover the bottom of the pan. Spoon the raspberry curd over the top and spread lightly with an offset spatula. Spread the remaining cake batter over the top of the curd carefully. Swirl gently with a butter knife.: The first layer of batter will look slightly matte as it settles into the pan, and the raspberry curd will glisten as you spoon it. Spread it lightly so it forms an even layer without mixing fully into the cake. When you add the final batter, it should cover but not bury the curd completely. Use a gentle swirling motion to create ribbons rather than blending everything into one uniform color. A common mistake is pressing the curd into the base too hard, which causes it to sink and make the cake soggy in spots, so be light handed.
Bake for 28-33 minutes, or until a toothpick comes out clean. Immediately press the egg shaped candies equally over the top of the cake (so each slice gets one egg). Let cool completely before serving.: As the cake bakes you will notice a faint sweet aroma and a golden edge forming around the pan. The center will feel springy when gently touched and the top should be lightly set. A clean toothpick indicates the interior is cooked but still moist. Pressing the egg shaped candies onto the warm surface helps them adhere without melting; they will glisten and create a festive finish. If you remove the cake too soon it may break, and if you leave it in too long it will dry out, so watch the bake time closely.