In a large pan, heat oil over medium. Lower the temperature and add onions. Simmer them until soft, or about 10 minutes. Add a teaspoon or a few of water (or broth) as you are simmering. (The onions and veggies shouldn't fry per se, but lightly stew.)
Add peppers. Continue simmering and stirring for about 10 minutes while adding a little bit of water (broth) at a time.
Add tomatoes and seasonings. Continue simmering and stirring for another 20 minutes. As in previous steps, add a little water (broth) at a time if needed. (Satarash is ready when the vegetables are completely soft, savory with sweet overtones, and a tiny bit stew-y, but not overly.)
Serve sataraš (satarash) immediately or pretty soon after it's made. Store in the fridge, in an airtight container for up to 48 hours. Reheat using your preferred method. Add a pinch of water or vegetable broth if needed when reheating.
Notes
Serving sizes:
If serving the dish as the main course, it serves 2. (Nutrition info above is for 2 servings.) If serving the dish as a side dish, it serves 3.