Grease a standard loaf pan or 8-inch round cake pan with butter and line it with parchment paper.
In a medium bowl, whisk together the 1 ½ cups oat flour and ½ cup almond flour, 1 tablespoon loose Earl Grey tea, 1 ½ teaspoons baking powder, and ¼ teaspoon fine grain sea salt.
In a large bowl, rub the 2 teaspoons freshly grated orange zest into the 1 cup granulated sugar until the oils release into the sugar. Then beat in the ½ cup unsalted butter and continue beating on medium speed until light and fluffy, about 3 minutes. Add the 2 large eggs one at a time and beat until combined, scraping the sides of the bowl as necessary. Add the flour mixture and ½ cup whole milk in three additions, beginning and ending with the flour.
Preheat the oven to 350°F. Spoon the batter into the prepared pan and smooth the top. Let the batter rest while the oven heats.
Place in the oven and bake just until a toothpick comes out with moist crumbs attached, about 40-45 minutes. Transfer to a rack to cool for about 15 minutes then turn the cake out onto the rack to cool completely.
Notes
Rub the zest into the sugar - This little trick works beautifully for all cakes made with citrus zest! When you rub the zest into the sugar, the oils are released, giving your batter even more flavor and fragrance.
Rest the batter - Make sure to rest the batter while the oven preheats so that the gluten-free flours hydrate. This will result in a better crumb.
Bring ingredients to room temperature - Let the ingredients sit on the counter a bit before you use them in the recipe. They will incorporate better into the batter if you take this step.
Oat floursubstitute - Substitute an equivalent amount of sorghum flour by weight for the oat flour.
Almond flour substitute - Swap tiger nut flour or another nut flour of your choice, or try teff flour by weight.
To make dairy-free - Use melted coconut oil in place of the butter and your favorite non-dairy milk in place of the whole milk.
Make refined sugar-free - Use coconut sugar in place of the granulated sugar.
Go less sweet - This cake is plenty sweet with 1 cup of sugar in the batter, so I don't add a glaze. You can reduce the sugar by ¼ cup to cut down on the sugar a bit.
Try lemon zest - Instead of the orange zest, add lemon zest to the batter.
Add chocolate - Add 1 cup of chopped, bittersweet chocolate to the cake.