Step 1

Place the pounded steak into a large baking dish. Season the steak with salt and pepper and cover it with milk. (Add a little extra milk if the steak is not completely covered.)

Step 2

Cover the dish and refrigerate for 8-12 hours.

Step 3

Heat the oil in a medium saucepan over medium-high heat. Add the minced onion and garlic, and saute until softened, about 5 minutes.

Step 4

Reduce the heat to medium and add the tomatoes, oregano, paprika, chile flakes, and salt. Bring the sauce to a simmer. Cook, stirring occasionally, until the sauce has thickened, 10-12 minutes.

Step 5

Remove the marinating meat from the refrigerator 1 hour before you want to grill it, to let it come to room temperature.

Step 6

Preheat grill to a medium-high heat.

Step 7

Drain the milk from the steak, discarding the milk. Pat the steak dry.

Step 8

Place the steak on your preheated grill and grill the first side for 5-7 minutes, uncovered.

Step 9

Flip the flank steak.

Step 10

Spread the cooked side with your prepared pizza sauce. Spread the mozzarella cheese over the sauce, and top with the tomatoes (and other toppings if desired).

Step 11

Cover the grill and cook for an additional 3-5 minutes, until the steak is done and the cheese has melted.

Step 12

Remove the steak from the grill and let it stand for 5 minutes before slicing, to let the juices settle.

Step 13

Garnish the matambre a la pizza with oregano to serve (if desired). Serve with roasted (or grilled) potatoes and grilled bread.