This delicious easy butter bean curry is based on one of my favorite Indian dishes, a tangy spiced dish served with fluffy flatbread. It's vegan, very easy to make, and super economical. If you have the spices to hand, you just need some butter beans, a large onion, two tomatoes, water, and some lemon juice for a meal that is truly more than the sum of its parts. You can use cooked or dried butter beans. Serve over fluffy basmati rice to soak up the delicious sauce.