Rinse the lentils under running water in a strainer. Sort through the lentils to pick out and remove any shriveled or discolored ones.
For less soft lentils
If you want some of the red lentils to retain their shape, while still being cooked through, combine the 1 cup lentils with 2 cups water in a pot or saucepan with a lid. Bring to a boil, then reduce heat to very low to maintain a simmer. Cover and cook for 5 to 8 minutes, stirring once or twice to promote even cooking. If the lentils are still not cooked through at 8 minutes, cook for a few minutes longer. Drain excess water before serving/using.
For softer lentils (puree-like)
To cook red lentils in the typical way, so that they break down into a mushy texture, combine the 1 cup lentils with 3 cups water in a pot or saucepan with a lid. Bring to a boil, then reduce heat to very low to maintain a simmer. Cover and cook for 5 to 8 minutes, stirring once or twice to promote even cooking. If the lentils are still not cooked through at 8 minutes, cook for a few minutes longer. Drain excess water before serving/using.
Notes
Seasoning ideas: Cook the lentils in vegetable or chicken broth with a bay leaf, salt and pepper, smashed garlic, thyme sprigs, and/or a cinnamon stick. After they're cooked, you can season them with extra virgin olive oil, salt, pepper, curry powder, cumin, chili powder, turmeric, cinnamon, or fresh herbs.
Storage: Store cooked red lentils in an airtight container in the fridge for 5 to 7 days or in the freezer for up to 6 months. If frozen, thaw in the fridge overnight before using or add to hot recipes directly from frozen.
You can add cooked red lentils to soups, baked goods, sauces, and dips.