Grill Pan Waffles

In a large bowl, whisk together flour, sugar, baking powder, baking soda, and salt. In a medium bowl, whisk together milk, melted butter, eggs, and vanilla. Add wet ingredients to dry and ingredients and mix until just combined.  Heat a medium grill pan over medium heat and spray with cooking spray. Add about ½ cup batter in center of pan. Cook until bubbles form around edges and waffles are easy to flip, about 3 minutes, then flip and cook 2 minutes more. Repeat with remaining batter.  Serve waffles warm with butter and maple syrup.