Roast Peppers: Flame-roast the bell and jalapeno peppers on a gas cooktop or under the broiler until the skin is blackened. Let cool for 5–10 minutes. Under a cool stream of water, peel the skin, remove seeds, and slice into strips. Set aside.
Infuse Spices: In a deep skillet over medium heat, add olive oil, paprika, chili powder, turmeric, and sliced garlic. Fry until the garlic turns a pale beige; this wakes up the aromatic oils.
Simmer: Add the roasted pepper strips, guajillo, and arbol peppers (if using). Add the cans of diced tomatoes. Cover and simmer for 30 minutes.
Reduce: Use a potato masher to break down any firm tomato chunks. Stir in the sugar. Cover and simmer on low for another 30 minutes, or until the liquid has significantly reduced into a thick paste.
Finish: Remove from heat. Drizzle with a little olive oil, sprinkle with salt, and serve at room temperature or chilled.