Preheat your oven to 350°F (175°C).
Grease a 9x5-inch loaf pan with oil or butter, or line it with parchment paper.
In a large mixing bowl, whisk together the gluten-free flour, baking soda, baking powder, ground cinnamon, and salt.
In another bowl, combine the granulated sugar, brown sugar, and vegetable oil. Mix until smooth, then add the applesauce, eggs, and vanilla extract. Stir until fully incorporated.
Gradually add the dry ingredients to the wet ingredients, mixing gently until just combined. Fold in nuts or dried fruits if desired.
Pour the batter into the prepared loaf pan and smooth the top with a spatula.
Bake for 50-60 minutes, or until a toothpick inserted into the center comes out clean.
Let the bread cool in the pan for about 10 minutes, then transfer to a wire rack to cool completely before slicing.