This dish is by far the best if you take the time to toast the spices from seed and grind them yourself. We make batches every month or so and enjoy the resulting spice mix in the mean time. It makes every dish so much more full of flavour.
Start with an onion and a dash of oil in a fry pan and cook for a few minutes. You can add garlic too if you like. While that's getting going you can strain your beans. Depending how big you want to make the dish you can add more veggies or more beans.
Then add either your spice mix (see link above) or ground spices from the pantry...you'll want paprika, cumin and coriander, and some chilli if that's what you like.
Once you've put the spices in you'll want some water handy to stop them burning once they've toasted...it can happen pretty fast and catch you out (no pun intended when the spices catch...#facepalm).
Next add your beans, tablespoon or two of tomato paste and depending how wet or dry you want your dish to end up, a tin or two of tomatoes. If you're going for a dry buddha bowl dish just go with the spices and tomato paste. If you're looking for more of a beans casserole type feeling add the tinned tomatoes too. Season to taste with salt and pepper and serve how you like. It's great with fresh coriander on top.