From How to Cook Everything.
1 1/2 Cup Lentils, Washed And Picked Over
2 Carrots, Peeled And Minced
1 Medium Onion, Minced
1 Cup Tomato (Canned Is Fine; drain First), Cored And Chopped
1 Teaspoon Dried Oregano (or Marjoram;1 Tbsp Fresh)
2 Tablespoon Olive Oil
1 Medium Onion, Sliced
1 Teaspoon Garlic, Minced
1 Pounds Pasta (Elbows, Shells, Or Similar)
Combine the lentils, carrots, minced onion, and water to cover in a large pot over medium heat. Simmer until the lentils are tender but not at all mushy, 20 to 30 minutes (some lentils may take even longer, but check frequently to avoid overcooking). Add the tomato, salt, pepper, and half the oregano, stir, and keep warm over low heat.(This sauce may be made up to this point and covered and refrigerated for a day or two ahead, or put in a closed container and frozen for several weeks.)Meanwhile, heat the olive oil in a medium skillet over medium-high heat for 1 minutes. Add the sliced onion and cook, stirring, until it begins to brown and become crisp, about 10 minutes.
Bring a large pot of water to a boil.When the lentils are done, salt the boiling water and cook the pasta until it is still quite firm and a bit chalky in the center. Drain it, reserving a cup or so of the cooking liquid. Stir the pasta into the lentils along with the garlic, the cooked onion, and the remaining oregano. Add enough of the pasta water to moisten the mixture. Cook for 2 or 3 minutes, or until the pasta is tender. Taste, adjust seasoning if necessary, and serve in a warm bowl.