Preheat the oven to 425°F. Place the 4 naan flatbreads on a large baking sheet.
Cook the 1 lb ground beef with the 1/2 tsp kosher salt and 1/4 tsp black pepper in a large skillet over medium-high heat for 7–8 minutes, breaking it into crumbles, until a food thermometer inserted into the center reads 160°F. Drain any excess fat.
Spread the 1/2 cup olive tapenade over the naan. Top with the cooked beef, 1 cup roasted red peppers, and 1 1/2 cups mozzarella.
Bake for 7–8 minutes, until the flatbreads are crisp at the edges and the cheese is melted.
Toss the 3 cups arugula with the zest and juice of the 1 lemon and 1 tsp olive oil. Top the flatbreads with the arugula and cut each into wedges.
