Wash and dry all produce. Preheat oven to 425 degrees. Halve, peel, and finely chop onion. Mince or grate garlic. Thinly slice scallions.

Heat a drizzle of oil in a large pan over high heat. Add ground beef and break up into pieces with a spatula or wooden spoon. Cook until browned, 4-5 minutes. Stir in Mexican spice blend and season with salt and pepper. Remove from pan and set aside.

Add onions, garlic, and a drizzle of oil to same pan over medium heat. Cook until softened, 4-5 minutes. Stir in 2 tsp Southwest spice blend (we sent more) and half the scallions. Cook until fragrant, about 30 seconds. Stir in diced tomatoes and ground beef. Season with salt and pepper.

Place a layer of filling in a small baking dish (ours is 11 x 7). Top with 2 tortillas, tearing to fit. (TIP: It's OK if tortillas don't cover filling completely.) Add a layer of Monterey Jack cheese. Repeat with three more layers, finishing with a layer of filling and cheese.

Bake casserole until melted and bubbling, 5-7 minutes. (TIP: For a golden and crispy top, heat broiler to high and broil casserole a further 2-3 minutes.) Meanwhile, halve lime. Halve grape tomatoes. Toss mixed greens and grape tomatoes in a large bowl with a squeeze of lime and a drizzle of olive oil. Season with salt and pepper.

Sprinkle casserole with remaining scallions. (TIP: If you have time, let rest a few minutes for cleaner slices.) Cut casserole into slices and serve with salad and a dollop of sour cream on the side.