In a small measuring cup, whisk together milk and lemon juice. Set aside for 5 minutes to allow milk to sour.
In a mixing bowl, sift together flour, sugar, baking powder, baking soda, and salt. Add sour milk, egg, and vegetable oil; mix until no lumps remain.
Heat a skillet over medium heat; spray with cooking spray. Use a ¼ cup measure to pour batter onto the hot skillet. Cook until bubble form on top of the pancake; flip and cook until golden brown. Serve hot.