Preheat oven to 350° F, line a muffin tin with some non-stick or foil liners
Mix flour, baking powder, baking soda, salt and cinnamon together in a separate bowl
In a large mixing bowl, cream butter and sugar until light and fluffy.
Add in bananas and mix until well-incorporated.
Add in eggs and vanilla. Mix until smooth.
Add in half of the dry ingredients and mix slightly. Then, add in buttermilk and mix slightly. Finally, add in the rest of the dry ingredients and mix until just incorporated.
Fill your muffin tin cups about 3/4 of the way (I use a 1/4 cup measuring cup for mine)
Bake at 350°F for about 15-20 minutes, or until a toothpick inserted comes out clean.
Let your banana muffins cool completely.
Then, remove the center from your muffins using a cupcake coring tool. Fill the centers with strawberry jam and replace the tops that were removed.
Enjoy!