Step 1

Heat oven to 350° F (177° C). Lightly butter a 5x5 inch baking dish with butter and set it aside.

Step 2

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.

Step 3

Mix in the egg, lemon juice, and vanilla extract, continuing to beat the mixture until these ingredients are fully incorporated and evenly combined.

Step 4

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.

Step 5

Next, add the dry ingredients to the butter and sugar combination. Mix everything together until all the ingredients are combined.

Step 6

Add the milk and mix until combined.

Step 7

Using a rubber spatula, gently fold in the blueberries.

Step 8

Pour the cake batter into the buttered baking dish and place the baking dish on a rimmed baking sheet to catch any possible spills.

Step 9

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.

Step 10

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.