Whisk together flour, baking soda, baking powder, sugar, salt, and lemon zest in a bowl.

In a separate bowl, lightly whisk egg yolks.

Whisk in buttermilk and ricotta cheese.

Combine the yolk mixture into the flour mixture until just combined.

In another bowl, whisk egg whites until stiff peaks form.

Gently fold egg whites into the batter.

Place 1/2 teaspoon of melted butter in each well of an ebelskiver pan.

Heat pan over medium heat until butter bubbles.

Pour 1 tablespoon of batter into each well.

Place 4 blueberries in the center of the batter and top with 1 tablespoon of batter.

Cook until the bottoms are golden brown and crispy, about 3-5 minutes.

Turn the pancakes over using skewers and cook until golden brown and crispy, about 3 minutes more.

Transfer to a plate.

Repeat with remaining batter and blueberries.

Dust with confectioners' sugar and serve warm.

For a savory variation, fill with chilled butter with herbs, grated cheese, or bacon/ham and omit powdered sugar.