In an 8-quart pot, heat oil over medium heat. Sauté carrots, stirring until they brown slightly, about 5 minutes. Add red onion and garlic. Season with salt, pepper, cumin, and oregano. Sauté until onion becomes translucent, about 5 minutes. Add bell pepper and celery; stir until the pepper softens, about 5 minutes. Remove from heat and pour in 1 cup vegetable stock plus canned tomatoes. Use an immersion blender to puree the ingredients in the pot. If needed, tip pot to submerge blender in the sauce. Add remaining stock, lentils, cinnamon, and bay leaf. Return to heat, cover partially to prevent splattering, and bring to a simmer. Cook for 30 minutes, until sauce thickens and lentils are cooked. Stir occasionally to prevent sauce from sticking to the bottom of pot. Remove from heat and stir in agave. In a tall pot, boil the pasta according to package instructions, then strain. For each serving of pasta, toss with 1/2 cup sauce. Serve on plates or bowls and grate Parmesan over pasta.