The sherry vinegar gives the relish lots of flavor, so choose a good one.
To prepare steak, cook the first 3 ingredients in a small nonstick skillet over medium heat for 45 seconds or until toasted. Place the peppercorn mixture in a spice or coffee grinder; process until finely ground.
Remove 1 chile from can; reserve remaining chiles and sauce for another use. Place peppercorn mixture, chile, 2 tablespoons vinegar, and the next 4 ingredients (vinegar through garlic) in a blender; process until smooth, scraping sides occasionally. Combine vinegar mixture and steak in a large zip-top plastic bag; seal and marinate in refrigerator 24 hours. Remove from bag; discard marinade.
Prepare grill or broiler.
Place steak on grill rack or broiler pan coated with cooking spray; cook 6 minutes on each side or until desired degree of doneness. Cut steak diagonally across the grain into thin slices.
To prepare the relish, heat a large nonstick skillet coated with cooking spray over medium-high heat. Add corn; sauté 5 minutes or until lightly browned. Remove from heat; stir in tomato and remaining ingredients except thyme leaves. Garnish with thyme, if desired.