Preheat oven to 450°F and combine beans, tomato, and 1 tablespoons pesto; mix well. Center 1/2 of bean mixture on each foil sheet.
Top each 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 under, leaving room for heat circulation inside packets.
Bake 16 to 20 minutes on a cookie sheet in oven. Serve with remaining pesto.
Grill: Preheat grill to medium-high and grill 14 to 18 minutes in a covered grill. Serve with remaining pesto.