1/4 cup FRENCH'S® Dijon Mustard
1/2 cup mayonnaise
1/4 cup pitted Kalamata olives
2 tsp. garlic
4 (4-in.) ciabatta rolls
1 cup arugula
1 cup julienne red onion
4 (4 oz.) tuna fillets
Combine mustard, mayonnaise, olives and garlic in food processor and process until smooth.
Grill tuna fillets on greased rack over medium-high heat, about 4 min. per side until just opaque in center.
Spread 2 tbsp. olive mixture on bottom half of each roll. Top with 1/4 cup arugula, 1/4 cup onion, and tuna fillet. Close with top half of roll.
Serve sandwiches with remaining sauce on the side.