Sift the flour, baking powder, baking soda and salt together in a medium bowl and set aside. Cream together the butter, sugar and lemon zest. Beat the ricotta into the butter mix until well combined. Beat in the egg. Add the milk and lemon juice – it’s going to look curdled. Add the dry ingredients to the wet ingredients and stir until just blended. Warning! It’s going to be very thick! Divide the batter equally among the muffin cups. Sprinkle the muffins with sugar. Bake until a toothpick comes out clean and they are a nice lightly golden color, approx 16-18 minutes. Remove the muffins from the pan and let them cool on a wire rack.