Make the red batter: In a medium bowl, whisk one box of cake mix with 2 eggs and ½ cup milk until smooth. Stir in red gel coloring a few drops at a time until bright red.

Bake the red cake: Pour the batter into a prepared pan, place in the air fryer basket, and cook at 320°F for 12–15 minutes, until a toothpick inserted in the center comes out clean.

Cut the hearts: Cool the red cake completely on a wire rack. Cut into ½-inch slices, then punch out shapes with a small heart-shaped cookie cutter. Set aside.

Make the green batter: In a large bowl, whisk the second box of cake mix with 2 eggs and ½ cup milk. Tint bright green with gel coloring.

Assemble: Line the second pan with parchment and spray lightly. Spread a thin layer of green batter over the bottom, then stand the red hearts in a tight row down the center, all facing the same direction. Pour the remaining green batter over the hearts.

Bake the green loaf: Air fry at 320°F for 12–15 minutes, until a toothpick inserted into the green cake (not a heart) comes out clean.

Decorate: Cool completely. Knead the fondant until soft, roll it into a rectangle on a powdered-sugar-dusted surface, and drape it over the loaf, smoothing the top and sides. Press on the heart sprinkles and refrigerate 30 minutes to set.

Serve: Slice crosswise so every piece reveals a red heart.