Preheat the oven to 375℉. Line a 12-cup muffin pan with paper liners and spray them lightly with nonstick spray.
In a large bowl, whisk together the flour, sugar, baking powder and salt. Make a well in the center. In a separate bowl, whisk together the ricotta, water, oil, zest, juice and egg. Add to the dry ingredients. Stir just until moist.
Use an ice cream scoop (or ⅓ cup measuring cup) to scoop the batter into the muffin cups. Bake 16 minutes, or until a toothpick inserted into the center of a muffin comes out clean. Cool before chowing down.