Preheat a nonstick pan. Combine flour, baking powder, nutmeg, salt and sugar in a small bowl. In a large bowl, whisk ricotta, eggs, milk, lemon juice and zest. Fold flour mixture into the wet ingredients until just combined. Gently fold in blueberries. Brush hot pan with butter. Pour about ¼ cup batter for each pancake onto pan and cook until light golden brown on both sides. Dust with powdered sugar before serving.