In a small mixing bowl combine flour, sugar, baking powder, and salt. In a separate large mixing bowl combine the ricotta cheese, eggs, milk, vanilla, lemon juice and zest. Whisk the flour mixture into the wet ingredients until just combined.
Heat an electric griddle to 350 degrees or alternately, place a large skillet over medium heat. Spray your cooking surface with non-stick cooking spray. For each pancake, measure out 1/4 cup of batter, pour on to the hot cooking surface and cook on both sides until light golden brown. Top each pancake with a small pat of butter. Repeat with remaining batter.
For the Blueberry Sauce:
Combine sugar and cornstarch in a medium saucepan. Gradually stir in water and place pan over medium heat. Add blueberries and cook, stirring, until mixture comes to a low boil. Continue to cook and stir for an additional 3 or 4 minutes, until thickened. Remove from heat and serve right away or cool to room temperature and transfer to an airtight container and refrigerate until ready to serve.
This sauce is delicious served either warm or cold over pancakes, waffles, oatmeal, Greek yogurt, ice cream, pound cake, etc. Store leftovers in an airtight container in the refrigerator for up to a week.