Broiled Halibut with Summer Herbs

Name: Broiled Halibut with Summer Herbs
Ingredients: 1 large piece of skinless halibut (about 1 1/2 pounds; preferably center-cut); 1 lemon, halved, plus wedges for serving; Kosher salt and freshly ground pepper; 1/2 cup mayonnaise; 2 tablespoons roughly chopped fresh chives; 2 tablespoons roughly chopped fresh dill; 2 tablespoons roughly chopped fresh parsley; 4 cups baby arugula (about 3 ounces); 2 tablespoons extra-virgin olive oil; 3 large heirloom or beefsteak tomatoes, sliced 1/2 inch thick