1½ tablespoons olive oil
2 medium onions, finely chopped
½ teaspoon sea salt, or more to taste
2 tablespoons balsamic vinegar, or more to taste
2 cups dried red lentils, rinsed
5 cups water
Freshly ground black pepper
Ground cayenne pepper
Pour the oil into a large skillet over medium heat. Once the oil shimmers, add the onions, stirring to coat; cook until the onions wilt, about 1 minute. Reduce the heat to medium-low; cook, stirring often, for 20 minutes. Add the ½ teaspoon salt and cook, stirring occasionally, until the onions are super soft and very sweet, 10-20 minutes or longer, if needed. Stir in the 2 tablespoons of vinegar during the last 2 to 3 minutes.
Meanwhile, combine the lentils and water in a large saucepan over high heat. Bring to a boil, then reduce the heat to medium or medium-low until barely bubbling around the edges (use a heat diffuser, if you have one, underneath). Partially cover and cook gently until the lentils are perfectly soft, about 40 minutes. The mash will be supple at this stage. If you'd like it stiffer, cook uncovered for a little longer.
Add the lentils to the onions, stirring to thoroughly blend; taste, and add salt and/or vinegar as needed. Season to taste with black pepper and cayenne pepper. Serve hot, warm or at room temperature.
Serves eight to 10 (makes 5 cups).
Cook's notes: In summer, top with chopped tomatoes; in winter, go with pomegranate seeds and yogurt. Serve as an appetizer, a side dish or part of a collection of small plates.
Nutrition values per serving (based on 10): 170 calories, 3 g fat (0 saturated) 28 g carbohydrates, 12 g fiber, 3 g sugar, 10 g protein, 0 cholesterol, 110 mg sodium.
Adapted from "The Heart of the Plate" by Mollie Katzen (Houghton Mifflin, 2013)