Carrot-Apple Snack Cake

1 stick (1/2 cup) unsalted butter, softened
2/3 cup plain yogurt
3/4 cup brown sugar
1/2 cup pure maple syrup
2 eggs
1 cup grated carrot
1 cup grated MacIntosh or other cooking apple, unpeeled
2 cups all-purpose flour (you can also use 1 cup each all-purpose and whole-wheat flour)
1 tsp each salt, baking powder, and baking soda
2 tsp cinnamon
1 tsp nutmeg
1 tsp vanilla

Preheat the oven to 375 degrees and lightly grease a 9-inch round cake pan.  Cream together the butter, yogurt, brown sugar, and maple syrup until smooth.  Add the eggs, one at a time, beating for about 30 seconds after each addition.  Fold in the grated carrot and apples.
In another bowl, combine the flour, salt, baking powder, baking soda, cinnamon, and nutmeg.  Gradually add the dry ingredients to the wet mixture, until everything is just combined.  Fold in the vanilla.  Pour the batter into the prepared cake pan and bake at 375 degrees for 40-45 minutes, until a toothpick inserted in the middle of the cake comes out clean and the top is springy to the touch.