Preheat oven to 400 degrees Fahrenheit. Grease a muffin tin or line with cupcake liners and set aside.
Make flax "egg": Mix flaxseed and water and set aside.
In a large mixing bowl, whisk together peanut butter, oat milk, and coconut oil. Then whisk in the flax egg.
In the same mixing bowl, add flour, cane sugar, baking powder, and salt. Whisk until just combined (some flour streaks are okay)
Scoop muffin batter into greased/lined cupcake tin almost to the top. (I like using an ice cream scoop for this step!)
Add 1 teaspoon jelly on top of the batter. Use a toothpick, swirl jelly into the muffin.
Bake for 18-20 minutes. Check doneness by sticking a toothpick into the center and it comes out clean.
Remove from oven and let cool.
Keep leftover muffins in an airtight container in the fridge for up to 4 days.They also freeze really well! Store the cooled muffins in an airtight zipper bag for up to 2 months in the freezer. Let them thaw in the fridge overnight before eating cold or reheating.Reheat PB and J muffins in the oven at 350 degrees for about 5 minutes. Or you can pop them in the microwave for 10 seconds to get nice and warm again.