Put the black-eyed peas, the halved onion, the carrots, and 3 bay leaves in a large pot. Cover it all with about 3 inches of water (you’ll need about 2 quarts). Put the pot over high heat, bring it to a simmer, then turn the burner to medium-low and continue to cook until the beans are tender, 60 to 90 minutes. Add 2 or 3 teaspoons of salt midway through the cooking. (Add more water if the water level goes below the beans.) Reserve 2 cups of the cooking liquid. Strain the peas, picking out and discarding the onion, carrots, and bay leaves.
While the peas are cooking, in a pot big enough to hold the beans, cook the bacon over medium-low heat until the fat is rendered and the bacon is browned. Add the medium diced onion and a three-finger pinch of salt. Cook over until the onion is softened and translucent and beginning to brown, 5 or 10 minutes. Add the cumin, pepper flakes, and black pepper, turn the burner to medium, and stir to combine the seasonings with the onion. Add the juice from the tomatoes. Then add the tomatoes, crushing them in your hand as if you were furious with them, dashing them, their brains squirting out between your fingers. (You could instead put them on a cutting board, of course, and roughly chop them, then scrape the tomato and juices into the pan with the onion.) Add the last bay leaf. Bring to a simmer and cook for 30 minutes or so to reduce and thicken the sauce.
Stir in the black-eyed peas, and cook to heat through. Add some or all of the reserved bean liquid to keep it juicy (add all of it if you’ll be chilling and reheating it). Taste. If it needs something, try a little more salt. Still need something? Try some fish sauce. Want it hotter? Add more pepper flakes. Too salty? Oops! Now you'll need to make a half batch with no salt and add it to this one! (Actually, I’ve always found the above recipe to be on the money.)
Serve immediately, or if it’s Wednesday and you’re not serving it till Saturday (the case here), cool then chill it in the fridge uncovered, then cover it when it’s cold. Reheat it slowly so as not to burn the bottom; add some water or some wine if it looks a little dry.
Serve with rice and some crunchy toasted and buttered bread, and garnish with pickled chiles if you have them!