Process onion and water in food processor until slushy, about 45 seconds.
Pass the onion slush through a fine mesh strainer over a large mixing bowl, pressing on the slush with a large rubber spatula. Discard the onion solids.
Wisk ketchup, apple cider, 3 tbl. apple cider vinegar, Worcestershire sauce, molasses, dijon mustard, chipotle chili, adobo sauce, and black pepper into onion liquid.
In a large saucepan, cook bacon over medium-high heat, until bacon is crisp.
Remove bacon with a slotted spoon.
Add garlic and chili powder to hot bacon fat and cook until fragrant, about 30 seconds.
Add onion-ketchup mixture to the saucepan and simmer for 15 minutes.
Off heat, add remaining 1 tbsp apple cider vinegar.
(Optional) Pulse cooked bacon is food processor until it is a fine powder and add to sauce.