1. In small sauté pan heat 1/4 cup oil over medium heat; add onion and sauté 2 minutes. Stir in garlic and continue to cook 1 minute. Whisk in white wine and bring to a boil. Remove from heat and stir in apple butter, mustard and pepper until smooth. Adjust seasonings with salt and pepper. Cool to room temperature. Cover and refrigerate until ready to use as directed.
2. Lay out pork tenderloins on sheetpans or in roasting pans and brush liberally with oil. Sprinkle with seasoning blend and salt and pepper, if desired. Cover and refrigerate for at least 2 hours before cooking.
3. Grill tenderloins to order until almost done (or roast in 400°F oven). Brush liberally with reserved Apple Butter BBQ Glaze and return to heat to finish cooking. Brush often during final cooking time with additional glaze, turning every 4 minutes to prevent glaze from scorching. Cook meat to an internal temperature of 160°F (cooking time will vary from 25-35 minutes, based on thickness of tenderloins and type of grill or temperature of oven). Remove from heat, brush again with glaze and let rest for 10 minutes.
4. To Serve: Slice meat into 1/2-inch thick slices, drizzle with any reserved glaze, and serve immediately. Serve with grilled or roasted garlic baby potatoes and other grilled or roasted vegetables.