Preheat the oven to 350°F (175°C) and grease a mini muffin pan with nonstick spray or line with mini muffin liners.
In a large bowl, whisk together the oat flour, baking powder, and cinnamon, then make a well in the center.
In a separate bowl, whisk the pureed baby food, mashed banana, and egg until combined.
Pour the wet mixture into the dry ingredients and stir until just combined, then fold in the grated carrot.
Divide the batter evenly among 24 mini muffin cups (or into 12 standard muffin cups for larger muffins).
Bake mini muffins for 13–15 minutes, or until a toothpick inserted in the center comes out clean. For 12 standard muffins, bake about 25–30 minutes.
Let the muffins cool before serving.