We mix the lamb with beef so the lamb flavor doesn't dominate. If assembling ahead, sprinkle with feta cheese just before baking.
1. Preheat oven to 375°.
2. Heat a large skillet over medium heat. Add oil to pan; swirl to coat. Add onion and next 4 ingredients (through beef); cook 14 minutes or until lamb and beef are browned, stirring to crumble. Add stock to pan; cook 3 minutes. Stir in salt, pepper, and tomatoes. Bring to a boil; reduce heat, and simmer 4 minutes, scraping pan to loosen browned bits.
3. Combine ricotta and rind in a small bowl. Spread 1 tablespoon ricotta mixture over one side of each lasagna noodle.
4. Spread 2 cups tomato mixture in bottom of an 11 x 7–inch glass or ceramic baking dish coated with cooking spray. Arrange 3 lasagna noodles, ricotta side up, over tomato mixture; top with 2 cups tomato mixture. Repeat layers twice, ending with 2 cups tomato mixture. Sprinkle evenly with feta cheese. Cover with foil; bake at 375° for 40 minutes. Remove foil; let stand 10 minutes. Sprinkle with parsley.