In a pan over medium-high heat, saute onion in oil. Once translucent, add beef and cook through, breaking up meat with a spoon. Stir marinara sauce into cooked meat, season with salt to taste, and set aside.

In a large mixing bowl, combine ricotta, egg, cauliflower rice, parmesan, parsley, salt, and pepper. Mix well to integrate and set aside.

Before or during lasagna prep, fill a dish with warm water and soak oven-ready lasagna noodles for 10-15 minutes.

Once softened, use kitchen shears to cut noodles to fit the size of your mini loaf pans or mini casserole dishes. (Save smaller noodle pieces and scraps to puzzle together as you assemble!)

To assemble each mini loaf pan lasagna for one: Add enough meat sauce to cover bottom of each dish. Top with a sheet of lasagna noodle, cut to size. Add ricotta mixture and spread evenly, followed by mozzarella cheese and a layer of spinach leaves.

Continue with another layer of meat sauce, a sheet of lasagna noodle, and ricotta mixture, spread evenly. (Repeat additional layers as needed/desired to fill your dish!)

Finish each mini loaf pan lasagna with a thin layer of meat sauce and more shredded mozzarella on top.

Wrap or cover prepared mini lasagnas and store in the fridge for up to 3 days, until ready to cook. Or, freeze for up to 1-2 months! Transfer frozen mini lasagnas to the fridge to thaw about 24 hours before you plan to cook.

When ready to cook, preheat oven to 400°F (200°C). Add mini lasagna dishes to a baking sheet, cover each dish with a small foil tent, and bake for ~20 minutes covered. Remove foil tent and continue to bake for another 10-15 minutes uncovered, until browned on top as desired.