Pat tuna steaks dry with paper towels. Arrange the tuna in a 13x9 inch baking dish. Mix lime juice, soy sauce, honey, chili sauce, and olive oil in a small bowl. Pour over the tuna. Turn the fish to coat with the marinade. Cover and refrigerate for 1 to 2 hours (no longer).
Prepare the grill to medium-high heat. Remove the tuna from the marinade. Pour the remaining marinade into a small saucepan and set aside. Grill the tuna 4 to 5 minutes on each side (or longer if the tuna is thick). Fish should be lightly browned on outside and pale pink on thickest part. 130 to 135° for medium-rare (considered the best way to enjoy it). Remove from the grill and let it rest.
Bring the reserved marinade to a boil over medium-high heat. Whisk the cornstarch with 2 tablespoons of water until smooth. Add to the marinade. Cook and stir until the sauce thickens, about 1 minute. Spoon the sauce over the tuna steaks and serve immediately.
Notes
Bottled chili sauce is found near the ketchup and sauces in your local market.