Preheat oven to 350°F. Roast tomatoes for 10 minutes. (If you have a gas stove, you may roast tomatoes over medium-high heat on a griddle.)
While the tomatoes are roasting, trim fat from pork roast and cut the meat into desired sized chunks.
Mix sea salt and ground black pepper, rub onto each side of the pork chunks. Set aside.
Place roasted tomatoes, half onion, paprika and cayenne pepper in a food processor/blender. Add a pinch of salt and 1/4 cup water. Blend until smooth. Taste and add more salt if desire.
Heat up a nonstick skillet on your stove. Melt butter and swirl. Use tongs to transfer pork chunks into the skillet, sear each side for 1 minute over medium-high heat.
Place half chopped vegetables (including the other half of the onion) on the bottom of a 4-quart slow cooker. Transfer seared pork into the pot. Cover with the other half vegetables and add bay leaf. Pour the smokey chili tomato sauce over all ingredients.
Cook on low for 8 to 10 hours. Discard bay leaf. Dish and garnish with parsley. Serve over rice.