Preheat oven to 350°F / 175°C. Line an 8×8 pan with parchment.
Whisk almond flour, 100 g sweetener, baking powder, salt, and ½ tsp cinnamon in a bowl.
Beat cream cheese until smooth. Add eggs one at a time, then melted butter, heavy cream, and vanilla. Beat until combined.
Fold dry ingredients into wet until just combined. Don’t overmix.
Mix swirl ingredients into a paste (50 g sweetener + 28 g butter + 12 g cinnamon).
Pour 2/3 of batter into pan. Dot 1/2 of cinnamon paste over batter. Pour remaining batter and dot with remaining paste. Swirl gently with a toothpick.
Bake 30–36 minutes; toothpick should come out mostly clean with a few moist crumbs. Tent foil if browning too quickly.
Cool 15–20 minutes, whisk glaze ingredients until smooth, and drizzle over cake. Chill 30–60 minutes for neater slices. Slice and serve.