Step 1Puree peppers with adobo sauce in blender or food processor. Put 2 teaspoons chipotle puree in large resealable plastic food bag with oil, juice, garlic and oregano. (Reserve remaining chipotle puree.) Add steaks, making sure they are thoroughly coated with marinade. Marinate at room temperature 30 minutes.
Step 1Heat oil in large nonstick skillet over high heat. Cook onions and peppers, uncovered, stirring often, 5 minutes. Add juice, chipotle puree, sugar and salt. Mix well. Cook, uncovered, until liquid has evaporated and onions are tender, about 5 to 7 minutes more. (Can be made a day ahead and refrigerated. To reheat, cook slowly over low heat until warm, adding water if mixture is too dry.) Serve hot.
Step 1Remove steaks from bag and discard marinade. Generously season with salt and pepper. Place on grill rack that has been sprayed with nonstick spray or greased with paper towels dipped in oil. Grill over medium-high heat, turning to cook both sides, until cooked as desired, about 4 to 5 minutes total for rare, depending on heat of grill. Transfer to cutting board. Cut across grain into 1/3-inch-thick slices.
Step 2To serve, arrange hot Pineapple-Sauteed Onions and Peppers on platter, top with sliced steaks and garnish platter with cilantro sprigs. Serve immediately with warm flour tortillas.