Recipe: 3 tablespoons maple syrup
1 1/2 tablespoons Dijon mustard
1 tablespoon fresh lemon juice
2 teaspoons extra-virgin olive oil
1/8 teaspoon ground red pepper
4 (5-ounce) tuna steaks, about 1 inch thick
1/2 teaspoon kosher salt
1/4 teaspoon freshly ground black pepper
Combine syrup, Dijon mustard, juice, oil, and red pepper in a shallow dish, stirring with a whisk. Reserve 4 teaspoons syrup mixture. Add tuna to remaining syrup mixture, turning to coat. Let stand 10 minutes, turning once after 5 minutes.
Heat a cast-iron skillet over medium-high heat. Coat pan with cooking spray. Remove tuna from marinade; discard marinade. Sprinkle tuna with salt and black pepper. Add tuna to pan; cook 90 seconds on each side or until desired degree of doneness. Remove tuna from pan. Cut across the grain into thick slices. Drizzle with reserved 4 teaspoons syrup mixture.