A large pot of plainly cooked lentils is one of the most useful things to have in an American refrigerator. Seasoned differently at each meal, it stops being the same dinner repeated.
The lentil is a neutral base
Cooked with only water, turmeric and salt, lentils are mild and take on whatever is added later. Nothing about the pot commits it to a particular dish.
This is the opposite of prepping finished meals, where the seasoning is fixed on day one and the fourth serving tastes exactly like the first.
It also means one cooking session covers several cuisines' worth of intent, since the base has not yet made any decisions.
Tempering is what changes the identity
A tempering is a small amount of fat heated with whole spices and aromatics, poured over the dish at the end. It takes a couple of minutes and dominates the flavor.
Mustard seeds with curry leaves produce something quite unlike cumin with dried chilies, and garlic browned in ghee produces a third dish from the same pot.
Because the tempering happens per serving, portions taken on different days can go in different directions without any advance planning.
Consistency is a second axis
Thinned with water the same lentils become a soup poured over rice; reduced further they become a thick side eaten with bread.
Blending part of the pot changes texture without changing ingredients, and folding in cooked vegetables converts it again.
Rice, flatbread and a raw salad each pair differently with the same bowl, which is a third source of variation that costs nothing.
What to buy in the US
Red lentils and yellow split peas are widely stocked in American supermarkets and cook down quickly without soaking.
Indian groceries carry a much wider range, including split pigeon peas and split mung, which behave differently in texture and cooking time.
Canned lentils work in a pinch but arrive already soft and salted, so they suit a quick side rather than a base intended to be seasoned several ways.
Storage and reheating discipline
Cool the pot promptly and refrigerate in portions rather than as one large mass, since a deep container holds heat in its center for a long time.
The FDA and USDA publish guidance on cooling and refrigerated storage times for cooked foods, and lentils are treated like any other cooked dish.
Freeze what will not be eaten within a few days. Lentils freeze well because there is no delicate structure to damage, and they thaw straight into a pan.