How to Make It
Prepare the Lasagna: Preheat oven to high broil with rack 8 inches from heat source. Coat bell peppers evenly in oil. Place on a baking sheet, and broil in preheated oven until charred, 12 to 15 minutes, turning occasionally. Transfer to a heatproof bowl. Cover tightly with plastic wrap, and let cool 15 minutes. Remove and discard skins and seeds. Cut bell pepper flesh into 1/2-inch-thick strips. Reduce oven temperature to 400°F.
Wring thawed spinach over a sink to remove excess moisture. Place spinach in a bowl, and add bell pepper strips and olives. Stir gently to combine. Stir together oregano, salt, and crushed red pepper in a separate small bowl. Set bowls aside until ready to use.
Bring a large pot of water to a rolling boil over high. Add noodles; cook 5 minutes (noodles will not be fully cooked). Drain; rinse under cold water until cool. Drain.
Spread 1/2 cup of the marinara sauce in bottom of a 9- x 13-inch baking dish. Top with 4 noodles. Layer with one-third of the spinach mixture. Sprinkle with 1/2 cup each of the feta, mozzarella, and ricotta. Sprinkle with one-third of the oregano mixture.
Spread with 1 cup of the marinara sauce, and top with 4 noodles. Layer with one-third of the spinach mixture. Sprinkle with 1/2 cup each of the feta, mozzarella, and ricotta. Sprinkle with one-third of the oregano mixture.
To make the next group of layers, repeat Step 5.
Top with remaining 4 noodles. Spread noodles with remaining 1 cup sauce; sprinkle with remaining 1 cup each feta and mozzarella.
Cover with aluminum foil; bake in preheated oven 40 minutes. Uncover; bake until lightly browned, 15 to 20 minutes. Let cool 10 minutes.
When ready to serve, prepare the Salad: Whisk together vinegar, oregano, mustard, honey, salt, and pepper in a bowl. Slowly whisk in oil. Toss together lettuce, cucumber, tomatoes, and vinegar dressing in a large bowl. Arrange Salad on top of Lasagna. Sprinkle Salad with feta.