Combine chicken breasts, onion, lime zest and juice, olive oil, spices, salt and pepper in a bowl. Using tongs, turn chicken breasts in bowl until thoroughly coated with marinade.
Cover dish and marinate in refrigerator for 4 hours or overnight for more intense flavor.
Pre-heat oven to 350 degrees. Put a large sauté pan or dutch oven over medium high heat and add a liberal amount of grapeseed oil. Using tongs, take chicken breasts out of the marinade and shake off most pieces of onion. Some will stick to the chicken breasts and that’s ok. Set marinade aside.
Sear large chicken breasts for three minutes on each side. For smaller or thinner chicken breasts, sear for two minutes per side.
Remove chicken breasts from heat and place into a baking dish. Pour the remaining marinade into the still hot sauté pan or dutch oven and deglaze with white wine. Stir marinade with wooden spoon, scraping up anything that sticks to the pan. Pour marinade over the chicken breasts and place baking dish in the oven uncovered for 30-35 minutes.
Transfer roasted chicken breasts to a cutting board and allow to rest for a few minutes. Shred or cut into thin strips.
Toast tortillas on baking sheet in oven, just until the edges just start to turn light brown. Take out of oven and sprinkle tortillas with shredded pepper jack cheese. Return to oven and toast again for a minute or two until cheese is melted. Be sure to keep an eye on the tortillas to prevent burning as this can happen quickly.
Transfer tortillas to a dinner plate and top with guacamole, chicken, and feta cheese. Garnish with pickled red onion, sliced radish, jalapeño pepper (if you like it spicy) and lime wedge. Enjoy!
