Step 1

Preheat the oven to 350°F (180°C) and line a 6-inch (15 cm) baking pan with parchment paper or grease it with oil.

Step 2

In a large bowl, whisk together Greek yogurt, egg, maple syrup, lemon juice, and vanilla extract until smooth.

Step 3

Sift oat flour, cornstarch, protein powder, and baking powder into the wet mixture. Gently fold until just combined — don't overmix.

Step 4

Pour the batter into the pan. Bake for 30-35 minutes, until the top is lightly golden, the center is set, and a toothpick comes out mostly clean (with a few moist crumbs, but no wet batter).

Step 5

Let the cake cool in the pan for 10 minutes, then transfer to a wire rack to cool completely before frosting.

Step 6

Add all ingredients to a bowl and mix until combined, adjusting sweetness to taste.

Step 7

Using a spatula or spoon, gently spread the frosting on top of the lemon loaf, once it has cooled.