Preheat the oven to 350°F (175°C). Grease a 9-inch round baking pan.
In a medium bowl, combine the flour, oats, baking powder, baking soda, and salt. Mix until blended.
In a separate bowl, cream together the brown sugar and butter until light and fluffy. Beat in the egg and vanilla extract. Add the dry ingredients to the wet ingredients and mix until blended.
Pour the batter into the prepared pan and bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean.
Let the cake cool in the pan for 10 minutes before transferring to a wire rack to cool completely.
Interesting Facts
Oatmeal is a great addition to cakes, adding extra texture and flavor.
This cake is great served with a dollop of whipped cream or a scoop of ice cream.
The cake can be stored in an airtight container for up to 3 days.