Preheat the oven to 325°F. Line an 8-inch square baking pan with parchment and lightly grease it.
Whisk the almond flour, coconut flour, baking powder, and salt in a bowl.
In a large bowl, whisk the eggs and powdered allulose until smooth. Whisk in the Greek yogurt, tahini, melted butter, and vanilla extract until creamy.
Fold the dry ingredients into the yogurt mixture until no dry streaks remain. Rest the batter for 5 minutes.
Spread the batter into the pan. Bake for 28 to 34 minutes, until the cake is golden and set in the middle.
Cool completely. Whisk the tahini, powdered allulose, and heavy cream into a smooth drizzle.
Spoon the tahini drizzle over the cake and sprinkle with toasted sesame seeds.