In a large bowl, whisk together the flour, baking powder, and salt. In a small bowl, combine the sugar and lemon zest. Rub together with your fingers until fragrant. Whisk into the dry ingredients.
In a medium bowl, whisk together the milk, lemon juice, eggs and vanilla. Add the wet ingredients to the dry ones, mixing only until combined. Stir in the chia seeds.
Heat a griddle pan or non-stick skillet over medium heat. Spray with cooking spray. Pour about 1/4 of a cup of pancake batter onto the hot griddle pan, spacing out the pancakes a few inches from each other. When the pancakes start to bubble up, flip and cook until pancakes are slightly golden brown.
Serve warm with butter, maple syrup or fresh fruit.