In a large bowl, mix minced meat with 1 egg, 1 tablespoon mustard, 1 cup breadcrumbs, 1 tablespoon paprika powder, salt, pepper, 1 finely chopped onion, and 1 finely chopped garlic clove until combined. Form the mixture into table tennis-sized balls. Place them in a baking dish, cover, and refrigerate while you prepare the other ingredients.
Cut the bell pepper into strips. Chop the remaining onion and garlic into large chunks. Quarter the tomatoes.
In a blender, combine the strained tomatoes (500 ml), ajvar (1 glass), half of the bell pepper strips, the quartered tomatoes, thyme, oregano, marjoram, basil, about 1 tablespoon olive oil, salt, and pepper. Blend for 1-2 minutes until smooth.
Uncover the meatballs and spread the remaining bell pepper strips between and around them. Pour the sauce over the meatballs.
Bake at 175°C (350°F) with convection heat for 35-40 minutes.