Place an oven rack 3 inches from heat source; preheat broiler. Brush bread with oil and broil, flipping once, until lightly charred on both sides, 1 to 1 1/2 minutes. Leave broiler on.
In a bowl, mix tuna with lemon zest and juice and reserved tuna oil; gently break into large flakes with a fork. Fold in peppers, olives and onion; mound onto toasted bread. Top with cheese. Broil just until melted, about 1 minute. Sprinkle with chives and almonds; serve.