Adjust rack to top position and preheat oven to 450 degrees. Wash and dry produce.

Halve tomatoes lengthwise. Halve jalapeño lengthwise, removing ribs and seeds for less heat. Halve and peel onion; thinly slice one half and cut remainder into chunks. Peel and halve garlic.

Place tomatoes, jalapeño, and onion chunks, cut sides up, on a baking sheet. Drizzle with oil and sprinkle with salt. TIP: Line sheet with foil first for easier cleanup.

Roast on top rack until browned and tender, 20-25 minutes.

While veggies roast, heat a drizzle of oil in a large pan over medium-high heat. Add sliced onion and beef*; season with Mexican Spice Blend, salt, and pepper. Cook, breaking up meat into pieces, until browned and cooked through, 4-5 minutes.

Turn off heat; transfer to a medium bowl and set aside to cool. Wipe out pan.

Carefully transfer roasted veggies (and any juices) to a blender along with garlic and cumin. Blend until smooth. TIP: To blend hot ingredients safely, work in batches if needed, filling blender only halfway. Remove center cap from blender lid, secure lid on blender, and hold a folded kitchen towel over the lid to allow steam to escape and protect yourself from splatters. Alternatively, you can use a food processor or an immersion blender.

Transfer salsa to a second medium bowl; season with salt and pepper to taste.

Stir half the mozzarella into bowl with beef mixture.

Heat a large drizzle of oil in pan used for beef over medium-high heat. Working one at a time, use tongs to briefly fry tortillas until beginning to blister, 5-10 seconds per side. Allow excess oil to drip into pan, then immediately dip tortillas into salsa in bowl; place on a clean work surface. TIP: You’re frying to soften the tortillas, not crisp them! If needed, add another drizzle of oil.

Divide beef filling between tortillas. Gently roll up tortillas; place, seam sides down, in prepared baking dish. TIP: It’s OK if the tortillas tear; no one will even notice after they’re covered in cheese and baked!

Spread remaining salsa evenly over top of entomatadas. Sprinkle with remaining mozzarella; bake on top rack until hot and bubbly, 10-12 minutes. Let rest for 2 minutes before serving.

Snip a small corner from sour cream packets and drizzle over top. Divide entomatadas between plates and serve.