A simple, moist oatmeal cake that's quick to put together — perfect for a lazy morning or an easy dessert. Rolled oats and warm spices give it comforting flavor, and it's finished with a light dusting of powdered sugar or a simple glaze.
Preheat the oven to 350°F (175°C). Grease a 9-inch round or square baking pan and set aside.
In a large bowl, whisk together the flour, rolled oats, granulated sugar, brown sugar (if using), baking powder, baking soda, salt, and cinnamon until evenly combined.
In a separate bowl, beat the eggs, then whisk in the melted butter, milk, and vanilla extract.
Pour the wet ingredients into the dry ingredients and stir gently until just combined. Do not overmix; the batter will be slightly thick.
Fold in the chopped walnuts if using. Scrape the batter into the prepared pan and smooth the top with a spatula.
Bake in the preheated oven for 30–35 minutes, or until a toothpick inserted in the center comes out clean and the top is golden.
Remove the cake from the oven and let it cool in the pan on a wire rack for 15 minutes. Then invert onto a plate or leave in the pan to cool completely.
Serve warm or at room temperature. Optionally dust with powdered sugar or drizzle a simple glaze before serving.
Notes
Store leftovers covered at room temperature for up to 2 days or refrigerate for up to 5 days. Reheat slices briefly in the microwave before serving.