Peel and finely chop the onion. In a bowl, mix the minced meat with the onion, mustard, tomato paste, egg, salt, and cayenne pepper until well combined. Shape the mixture into approximately 12 balls.
Prepare a muffin tin by placing paper muffin cases in each cup.
Place two slices of bacon on top of each other. Position a meatball in the center and fold the four ends of the bacon over the ball to wrap it completely. Place each wrapped meatball in a paper case, seam-side down.
Bake in a preheated oven at 180 °C (350 °F) with top and bottom heat for 30-45 minutes until golden brown.