In a medium skillet over medium heat, cook the diced bacon until crispy, stirring occasionally. While the bacon is cooking, line a plate with paper towels.

Using a slotted spoon, transfer the cooked bacon to the lined plate. Leave about ¼ cup of bacon grease in the skillet and carefully discard the rest.

Reduce the heat to medium-low. Add the diced onion to the skillet and cook, stirring often, until softened and beginning to caramelize.

Add the finely diced pineapple to the skillet with the onion. Continue cooking, stirring frequently, until the pineapple releases its juices and begins to soften, about 10 minutes.

Add the light brown sugar, apple cider vinegar, maple syrup, chili powder, kosher salt, and red pepper flakes (if using). Stir to combine.

Return the cooked bacon to the skillet and stir everything together.

Allow the mixture to simmer over low heat for 20 to 30 minutes, stirring occasionally, until thickened to a jam-like consistency. If the mixture seems too loose, continue cooking until most of the liquid has evaporated. The jam should be thick and glossy.

Let cool slightly before serving. Serve warm or refrigerate and gently reheat before using.