Heat oven to 350° F (177° C). Lightly butter a 5x5 inch baking dish with butter and set it aside.
In a medium-sized bowl, blend the butter and sugar with an electric mixer on medium speed until the ingredients are thoroughly combined, which usually takes about 2 minutes.
Mix in the egg, lemon juice, and vanilla extract, continuing to beat the mixture until these ingredients are fully incorporated and evenly combined.
In a separate small bowl, combine the flour, baking powder, and salt. Use a whisk or a fork to mix these dry ingredients together until they are well blended.
Next, add the dry ingredients to the butter and sugar combination. Mix everything together until all the ingredients are combined.
Add the milk and mix until combined.
Using a rubber spatula, gently fold in the blueberries.
Pour the cake batter into the buttered baking dish and place the baking dish on a rimmed baking sheet to catch any possible spills.
Bake the cake for 40 to 45 minutes, or until the top of the cake turns golden. To ensure that the cake is baked thoroughly, insert a toothpick into its center. The cake is done if the toothpick comes out clean, indicating that the batter is fully cooked through.
Remove from the oven and let the cake cool for 10 to 15 minutes before slicing. Top with powdered sugar if desired and enjoy the cake either warm or at room temperature.
Notes
Expert Tips
Read through the entire recipe and the Ingredient Notes section of the post and gather your ingredients. We provide a lot of information within the body of this recipe post to ensure that your blueberry cake comes out perfectly every time. This cake comes together quickly so it's a good idea to fully understand the recipe and have everything ready before beginning.
Measure Accurately: For best results, measure your ingredients precisely. This is so important. To measure flour correctly, stir the flour in its container with a spoon. Then, use a spoon to scoop flour into a dry measuring cup and slightly overfill. Then, use the back of a knife or other straight-edged utensil to level the flour across the cup. Do not scoop the flour. When you scoop, the flour gets packed too tightly and you will end up with more flour than the recipe calls for.
Don't Overmix: Stir your ingredients until just combined to avoid a dense cake.
Check for Doneness: Use a toothpick to check if your cake is done. If it comes out clean or with a few crumbs, it's ready.