Line a 12-cup muffin tin with liners and do a quick spray with cooking spray to keep the muffins from sticking.
In a medium bowl, whisk together the oatmeal, applesauce, milk, egg, vanilla, butter and brown sugar. In a large bowl, whisk together the flour, baking powder, baking soda, cinnamon, and salt.
Make a well in the center of the flour and pour in the applesauce mixture, stirring until just combined (be careful not to overmix). The batter texture will be wetter than other muffin batters.
Distribute the batter evenly among the 12 muffin cups (these muffins don’t rise very much, so go ahead and fill up the muffin cups). Bake for 15-20 minutes, until a toothpick inserted in the center, comes out clean. Be careful not to overbake or the muffins will be dry.
Notes
Slightly adapted from this recipe.I switched to brown sugar.