In a medium saucepan, combine the lentils, water, fennel seeds, and salt.
Bring to a boil; Reduce heat, cover, and simmer 30-40 minutes, or until lentils are very tender and most of the liquid is absorbed. Set aside.
Meanwhile, cook lasagna noodles according to package directions. Drain the noodles and rinse under cold water.
Mix the lentils with tomato sauce, sugar and basil.
Over medium-high heat, cook the onions and garlic in 1 + 1/2 tablespoons oil until tender, about 5-7 minutes.
Turn the onions into a bowl and set aside.
Add remaining 1/2 tablespoon oil and zucchini to skillet and cook, stirring, until zucchini is tender, about 8 minutes.
Preheat the oven to 200 degrees. Lightly grease in a baking dish.
Place half of the lasagna noodles on the bottom of the baking pan.
Lay the zucchini slices evenly over the noodles, then spread half the lentils over the zucchini and half the cheese over the lentils.
Top with remaining noodles, then onions, and finally with remaining lentil mixture.
Bake, covered, 30 minutes or until heated through.
Five minutes before lasagna is done, uncover and sprinkle with remaining cheese.
