Preheat oven to 450 F. Line a large baking sheet with parchment paper to prevent sticking.
Starting with one bell pepper upside down on a cutting board, slice downward, one side at a time, using the peppers natural creases as a guide for where to slice. You should end up with 4 slabs.
Carefully remove and discard the stem, ribs, and seeds. Repeat with remaining bell peppers.
Transfer the pepper slabs to the prepared baking sheet and place skin side facing up, in a single layer, leaving space in between each.
Place the pan in the preheated oven for 30 minutes, rotating the pan in the oven halfway through roasting. The tops should be dark, blistering, and easily pierced with a fork.
Transfer cooked peppers to a medium sized bowl and immediately place a plate over the top to trap the steam. Set the bowl aside to cool for 15 minutes.
Once cooled, use your hands to remove the skin from the peppers and discard. Place peeled peppers in a mason jar and keep in the fridge for up to 7 days.