Preheat your oven to 350°F (175°C) and lightly grease a 9-inch round cake pan or line it with parchment paper.
In a large mixing bowl, combine the rolled oats, baking powder, baking soda, cinnamon, nutmeg, and salt. Mix well.
In another bowl, whisk together the grated carrots, applesauce, honey or maple syrup, Greek yogurt, eggs, and vanilla extract until fully combined.
Gradually add the wet ingredients to the dry ingredients, stirring until just combined. Be careful not to over-mix.
If desired, fold in the chopped walnuts or pecans and raisins.
Pour the batter into the prepared cake 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.
Allow the cake to cool in the pan for 10 minutes before transferring it to a wire rack to cool completely.
Notes
Dust the cooled cake with powdered sugar and garnish with grated carrots and walnuts for an appealing finish. Serve slices with Greek yogurt for added creaminess.