Peel the onion and garlic, finely chop and mix with mayonnaise. Season with salt and pepper. Wash the pork, dry it and cut it into 5×5 cm pieces. Put it in a bowl, pour the prepared mayonnaise marinade, mix thoroughly and leave for 40 minutes.
Remove the pork from the marinade, wipe with napkins. String on 4 skewers and grill for 20-25 minutes. Serve with ketchup.