Preheat your oven to 350°F (175°C) and prepare a 9×5-inch or 8×4-inch loaf pan with floured cooking spray or grease and flour it.

In a large mixing bowl, whisk together the egg, light brown sugar, coconut oil, granulated sugar, sour cream, and vanilla extract until fully combined.

In another bowl, combine cinnamon, nutmeg, flour, baking powder, baking soda, and salt (if using) and mix well.

Gradually add the flour mixture to the wet ingredients, folding gently to combine without overmixing.

Fold in the grated carrots and apples until just combined.

Transfer the thick batter into the prepared loaf pan, smoothing the top.

Bake in the preheated oven for about 45 to 52 minutes, or until the top is golden and a toothpick comes out clean or with a few moist crumbs.

Let the bread cool in the pan for 15 minutes, then turn it out onto a wire rack to cool completely before slicing.