Mujadara is an incredibly filling and simple dish to make. This version from Epicurious suggests that you cook the onions for 15-20 minutes. I usually only make this recipe on the weekend when I have a lot of time to be in the kitchen, allowing the onions to cook for 45+ minutes at a very low heat. If you resist the urge to stir them, they will caramelize beautifully.
I like to serve this dish with a side of minted cucumber salad. I usually just wing this one, combining chopped cucumber, tomato, mint, parsley, lemon juice, olive oil, and salt. If you like working from recipes, this one from Taste of Home seems great!