In a large pot, combine the lentils, carrots, half of the chopped onion, and enough water to cover.
Bring to a simmer over medium heat and cook until the lentils are tender but not mushy, about 20-30 minutes.
Stir in the tomatoes, a generous pinch of salt and pepper, and half of the marjoram.
Continue to simmer for another 10 minutes to allow the flavors to meld.
Keep the sauce warm over low heat.
While the sauce simmers, bring a large pot of salted water to a boil.
In a separate skillet, heat 2 tablespoons (30 ml / 1 fl oz) of the olive oil over medium-high heat.
Add the remaining onion and cook, stirring often, until it begins to brown and crisp, about 10 minutes.
Cook the pasta in the boiling water until al dente (still firm).
Drain the pasta, making sure to reserve about 1 cup (240 ml) of the starchy cooking water.
Add the drained pasta directly to the pot with the lentil sauce.
Stir in the minced garlic, the crispy onions, the remaining marjoram, and the final tablespoon of olive oil.
Add a splash of the reserved pasta water to moisten the mixture and create a saucy consistency.
Cook for 2-3 minutes, stirring constantly, until the pasta is perfectly tender and coated in the sauce.
Taste, adjust seasoning with more salt and pepper if needed, and serve immediately in warm bowls.
Adjust the liquid to your liking.
Add more pasta water or some vegetable broth to create a soupy 'Pasta e Fagioli' style dish.
