Preheat the oven to 375°F and grease a 12-cup muffin tin with oil or line it with cupcake liners.
First, in a large bowl, rub the zest of 1 lemon into 1 cup granulated sugar until fragrant. Whisk in the 2 cups oat flour, ¼ cup almond flour, 1 ½ teaspoons baking powder, ½ teaspoon baking soda, and ½ teaspoon fine sea salt.
In a medium bowl, the ¼ cup vegetable oil with 2 large eggs an ½ cup Greek yogurt until combined. Whisk and stir in the dry ingredients, then fold in the 1 ½ cups blueberries. The batter will be quite thick.
Use a ¼ cup measure to scoop the batter into the prepared muffin cups. Rest the batter for 20 minutes.
Bake the blueberry muffins for 18 to 22 minutes, until a cake tester inserted in the center of one comes out clean. Remove from the oven, cool in the pan for 5 minutes, then turn out onto a rack to cool completely.
Notes
Grease the muffin tin very well. Muffins that stick to the pan make me so sad! Be sure to really grease the muffin tin with oil or non-stick spray so that the muffins release easily. Or, use muffin liners.
Rub in the lemon zest. Rubbing the lemon zest into the sugar as the first step is the key to super lemony muffins. This releases the citrus oil and infuses the muffins with flavor.
Don't substitute for a mix. I know it seems easier, but you'll truly love the texture that comes from the oat and almond flours. If you must, though, give my homemade gluten free flour blend a try.
Cool completely. As noted, these muffins are very soft straight out of the oven. Let them cool fully so that the crumb sets.
Make ahead. For a firmer texture, bake the muffins the night before you plan to serve them and store them in an airtight container on the counter.