Preheat the oven to 250 degrees F (120 degrees C) and set a small cookie sheet in the oven.
In a medium mixing bowl, combine Gluten-Free All-Purpose Flour (1 1/3 cup), Baking Soda (1/2 teaspoon), Baking Powder (1 teaspoon), Salt (1/2 teaspoon), and Ground Cinnamon (1 teaspoon). Whisk together with a fork or whisk to fully combine.
In a separate small bowl, add Oat Milk (1/2 cup) and Distilled White Vinegar (1 tablespoon), allowing to sit up to five minutes.
Meanwhile, in a large mixing bowl, beat Large Egg (2) with Pure Maple Syrup (1 tablespoon). After five minutes, whisk in milk and vinegar mixture into the bowl of eggs and syrup.
Gradually add dry ingredients to the wet ingredients in 1/2 cup increments, whisking to combine.
Once ingredients are fully combined and you have whisked away any clumps of flour, heat a greased skillet on the stovetop.
Using a 1/4 cup measuring cup, ladle the batter into the hot skillet. Once pancake batter begins to bubble, flip it using a spatula. Cook approximately 2-3 minutes on each side or until golden brown.
Place the cooked pancake onto the baking sheet in the oven to keep warm while you repeat the process with the remaining batter.