1. Place garlic, white wine and salt in blender; pulse until thoroughly blended. Whisk softened butter and slowly incorporate garlic and wine mixture. Reserve at room temperature for later use.
2. Sauté onions in corn oil in large skillet over high heat for 2 minutes until they begin to turn deep brown. Add 1/2 cup water to skillet and lower heat to medium-low. Cook and stir, scraping bits from bottom of pan, for 15 minutes until water has evaporated and onions are caramelized. Season to taste with salt and pepper.
3. Using a meat mallet, pound pork steaks until 1/2-inch thick; place in 1 gallon resealable plastic food storage bag. Pour remaining 1 cup water, soy sauce and pineapple juice over pork; seal bag and lay flat in refrigerator for 30 minutes, turning occasionally.
4. Heat charcoal or gas grill for indirect cooking at 300°F. Lightly grease grill grates.
5. Remove pork from marinade and place on grill over indirect heat for 4 to 6 minutes per side until internal temperature reaches 145°F to 160°F. Remove steaks from heat and brush garlic butter on both sides. Let stand 5 minutes; slice into 3-inch long thin strips.
6. While grill is still hot, reheat caramelized onions in its skillet and grill tortillas individually. Wrap 4 tortillas at a time in aluminum foil with a little garlic butter.
7. Serve fajitas with caramelized onions, guacamole, sour cream, pico de gallo and shredded cheese.