Finely dice the onions, peppers and bacon. Leave out the fat bacon and sear the pork belly and onions in it. Add paprika.
Add tomato paste and braise for a dark color. Deglaze with broth and add ketchup. Season to taste with the spices and let simmer covered for a while (I usually leave it on the fire for 2-3 hours). Finally, use the hand blender to make a smooth sauce.
The longer the sauce simmer, the better it tastes. It tastes even better when warmed up.