Step 1

Preheat oven to 350 degrees F (175 degrees C). Line 2 cups in a muffin pan with paper liners.

Step 2

Whisk egg white and sugar together in a bowl; stir in melted butter and vanilla extract until smooth. Add flour, baking powder, and salt and mix well. Add milk and mix until smooth. Divide batter equally between 2 prepared cups in muffin pan.

Step 3

Bake in preheated oven until cake is set, 10 to 12 minutes.