Heat oven to 400°F. Line a sheet pan with foil and set a rack on top.
Arrange bacon pieces on the rack in a single layer. Bake until starting to crisp at edges, 12–15 minutes.
Melt butter in a saucepan over medium heat. Stir in brown sugar and maple syrup; simmer until bubbling, about 3 minutes.
Whisk in warm cream, vanilla, kosher salt, and cayenne. Cook, stirring, 1–2 minutes until smooth and glossy.
Transfer par-baked bacon to a bowl. Toss with about two-thirds of the maple caramel and the pecans to coat.
Return coated bacon to the rack and bake until deeply glazed and crisp, 6–8 minutes.
Drizzle with remaining caramel. Sprinkle with flaky salt and black pepper. Cool 5 minutes before serving.