Slightly tart apple butter laced with cinnamon, cloves, and allspice is sandwiched between brown sugar, cinnamon, and oatmeal streusel for an easy-to-make dessert that is not too sweet. Add in a few pecans or walnuts to elevate that streusel just a bit.
Combine oats, flour, sugar, salt, and cinnamon in a medium-sized bowl.
With your fingers, work the butter into the flour and oats mixture until all the dry ingredients are incorporated into the butter.
Remove and set aside two cups of the butter/flour mixture.
Press the remaining butter & flour mixture into the parchment paper-lined baking pan, working it into the corners.
Spread two cups of apple butter over the crust.
If using nuts, gently toss the nuts with the remaining streusel topping.
Spread the streusel topping over the apple butter.
Bake for 30-35 minutes until streusel begins to brown.
Let cool in pan.
Remove bar by lifting parchment paper out of the pan.
Cut bars.
Serve immediately or store. See notes for make-ahead and storage tips.
Notes
You can make these apple butter oatmeal bars ahead of time and they'll still be fantastic. You have options:
Prepare and bake as written. The bars will keep at room temperature for two to three days. After that, store them in the fridge for up to five days.
Prepare and bake as written. Let the bars cool, and then slice them. Once sliced, transfer them to an airtight container and store them for up to two months. Depending on how 'airtight' your airtight container is, you may want to wrap them in aluminum foil or plastic wrap before putting them in the container.
Prepare up until baking. Wrap well the baking tray with aluminum foil or plastic wrap and freeze. Thaw in the refrigerator for twelve hours, and then let the baking dish come to room temperature before baking as instructed.