Preheat oven to 450 F. Combine tomatoes, and 2 tablespoons pesto; mix well. Center 1/4 of mixture on each foil sheet. Top with one halibut steak; drizzle with lemon juice. Sprinkle halibut with lemon pepper. Top with lemon slices. Bring up sides of foil and double fold. Double fold ends to form four packets, leaving room for heat circulation inside packets. Bake 16 to 20 minutes on a cookie sheet in oven. Serve with remaining pesto.