Preheat oven to 350° Fahrenheit. Lightly grease loaf pan with cooking spray, avocado oil, or butter and set aside.
Crack eggs directly into large mixing bowl. Add white sugar, brown sugar, and vanilla extract to bowl and whisk until ingredients are fully combined.
Add unsweetened almond milk and avocado oil to mixing bowl. Whisk until ingredients are fully combined with sugar mixture.
Add pumpkin purée to bowl and whisk until purée is fully incorporated. Set bowl aside.
Add gluten-free flour, baking soda, baking powder, salt, pumpkin pie spice, and cinnamon to second mixing bowl. With dry whisk, mix dry ingredients together until thoroughly incorporated.
Gradually, in small increments, pour flour mixture into sugar mixture, whisking well between each addition to thoroughly incorporate dry ingredients. Continue adding and whisk until all dry ingredients have been combined with all wet ingredients.
Carefully pour bread batter mixture into greased 9x5 loaf pan. Use spatula to spread batter evenly into all corners of pan and to smooth top of loaf.
Loosely cover loaf pan with aluminum foil, then place covered loaf pan in preheated oven. Bake bread, covered, 30 minutes.
After 30 minutes, carefully remove loaf pan from oven. Remove and discard aluminum foil, then return loaf pan to oven. Bake bread, uncovered, 30 minutes.
After baking bread 30 minutes uncovered, carefully remove loaf pan from oven and use toothpick (or knife) to check doneness of bread. Insert toothpick into center of loaf, then remove toothpick. Toothpick should come out completely clean or with very few crumbs. If needed, return bread to oven and bake 5 minute more, then test doneness again. Repeat as needed until bread is fully baked, but be careful not to overbake.
When bread is ready, carefully remove loaf pan from oven and set aside to cool 10 minutes.
After 10 minutes, transfer bread from loaf pan to cooling rack (see Notes). Let pumpkin bread cool on wire cooling rack at least 30 minutes.
Just before serving bread, lightly dust powdered sugar over top of loaf. Slice bread loaf into 8 to 12 slices as desired, and serve.