Cut the pork belly into pieces approximately 5 cm in size.
Heat oil in a large pan over medium-high heat and fry the pork pieces for 8-10 minutes until browned on all sides.
Add the chopped garlic, onion, and pesto. Cook for 2-3 minutes until softened and fragrant. Season generously with salt and pepper. Do not skim off the fat that renders from the pork—it will help bind the sauce and improve the flavor.
Add the canned tomatoes with their juice. Reduce heat to low and simmer uncovered for 2 hours, stirring occasionally and adding water a little at a time to prevent the mixture from drying out.
Add the tomato sauce and stir well. Continue simmering on low heat for 30 minutes.
Add the cherry tomatoes and simmer for 15 minutes until softened.
Verify the pork has reached an internal temperature of 63°C (145°F). Taste and adjust seasoning with salt and pepper as needed. Serve with pasta or white rice.