In small sauce pan combine all ingredients except the shrimp and bring to boil. Reduce heat and simmer for 5 to 10 minutes until liquid is reduced by half. Pour through fine strainer, reserving liquid and chill until cool. Pour 2/3 of marinade over shrimp reserving remaining marinade for stew (recipe to follow). Let shrimp marinate in covered container in refrigerator for 1 to 2 hours- (Tip: Marinade can be prepared ahead of time and shrimp can marinate in refrigerator for up to 48 hours before cooking and serving).
For Stew: Core and dice tomato into 1/2-inch cubes, removing seeds. Cut red potatoes into 1/2-inch cubes and blanch until tender (approximately 4 minutes). In a sauté pan, heat up the reserved marinade until boiling. Once boiling, add potatoes, tomato, red onion and cilantro. Reduce sauce by 3/4 then add citrus segments.
While sauce is cooking, remove shrimp from marinade. Discard used marinade. On char broiler or grill top, grill shrimp for approximately 2 minutes on each side. Serve shrimp on bed of rice with stew ladled on top.