Combine arugula, watermelon, tomatoes, bell pepper, and onion in a bowl; set salad aside.
Whisk together flour and next 3 ingredients in a shallow dish until blended; set aside. In a shallow bowl, whisk egg whites with salt until blended.
Dip crabs into egg whites, then coat in flour mixture, patting off excess.
Heat 2 tablespoons oil in a large nonstick skillet over medium-high heat. When oil is hot, add half the crabs, top-side down; sauté 2 to 3 minutes per side, until golden, adding more oil to skillet, if needed. Drain crabs on paper towels, then transfer to a baking sheet in a 200° oven to keep warm. Repeat with remaining oil and crabs.
Toss salad with 1/2 cup Smoky Tomato-Balsamic Dressing, and divide among 4 plates. Cut crabs in half, and top each salad with 4 halves.
"Let's take inspiration from the color of this dish's paprika and watermelon and opt for similarly pink-hued dry rosé. But color is not the only justification for this underappreciated summery wine. A good rosé, such as Château Routas Rouvière ($9) or Bonny Doon Vin Gris de Cigare ($8), will have plenty of red berry charm to complement this meal's fruity freshness. And if you use the spicy version of paprika or ground chile, these chillable rosés will soothe any sting you may sense." --Mark Oldman