1. Preheat oven to 425 degrees. Grease a rimmed baking sheet with cooking spray AND line with parchment paper. Set aside.
2. Combine 2 cups blueberries, the lemon juice, and 2 Tbsp. granulated sugar in a medium bowl. Let stand 15 minutes or so until juices get a little syrupy.
3. Combine flour, baking powder, and salt in another medium bowl.
4. In a large bowl, whisk egg yolks, ricotta cheese, remaining 6 Tbsp. granulated sugar, 6 Tbsp. melted butter, the letter zest, and milk to blend.
5. In a third medium bowl, beat egg whites with a mixer until soft peaks form.
6. Gradually add dry ingredients to the wet ingredients, whisking until smooth.
7. Fold in egg whites.
8. Spread batter in prepared pan, smoothing top with a spatula.
9. Evenly sprinkle blueberry-sugar mixture on top.
10. Bake until center is set and springs back when touched, 12 - 14 minutes. Remove pancake from oven. Set oven to broil (do not move rack from the middle shelf).
11. Brush remaining 2 Tbsp. of melted butter over the top of the pancake. Broil until golden brown (2 minutes - no longer!)
12. Cut panckae into 12 squares. Stack 2 pancakes per serving, dollop with whip cream, and put remaining blueberries on top, and dust with powdered sugar. Maple syrup is optional, serve on the table if guests want more sweetness.