Preheat your oven to 350ºF and line a baking sheet with parchment paper (for baked pancakes) or preheat a skillet over medium-low heat on your stove top (for skillet pancakes).
In a large bowl, whisk together the aquafaba and cream of tartar until foamy, about 1 to 2 minutes.
Add in the oat flour, 3 tablespoons of the sugar, baking powder, oil, water, and salt and stir until a smooth pancake batter is formed. Stir in the vinegar last, which will react with the baking powder, adding a little extra fluffiness to the pancake batter. Taste the batter and add 1 more tablespoon of sugar, if desired. (My family prefers them a little sweet.) This batter will thicken as it rests, so feel free to add extra water, just 1 teaspoon at a time, if it thickens while cooking the pancakes to help make it pour-able again.
FOR BAKED PANCAKES: Pour the batter 1/4 cup at a time onto the lined baking sheet. It should spread into small pancakes, so leave room for them to spread a bit when baked. Bake at 350ºF until the centers feel firm to a light touch, about 8 to 10 minutes. There's no need to flip them this way, and the whole batch can cook at once.
FOR SKILLET PANCAKES: Grease the preheated skillet, and pour 1/4 cup of the pancake batter into the center. Wait for the middle of the pancake to bubble, about 4 to 5 minutes on medium-low heat. (If the heat is too high, they can burn-- just like traditional pancakes!) Use a spatula to flip the pancake when it looks sturdy enough, then cook on the other side for another 3 to 4 minutes. Remove from the pan, and repeat with the remaining batter, greasing the pan each time to help prevent sticking.
Serve the pancakes warm, with fruit and/or maple syrup, as desired.