Preheat the oven to 350°F(177C°). Line baking sheet with parchment paper or silicone baking mat. Set aside.
Peel the apple and grate. When you grate the apple, there will be some excess juice left. Leave that juice as grated apple still have lots of juice and make these cookies soft.
Place the grated apples, lemon zest and cinnamon into a medium mixing bowl and mix. Add the peanut butter and mix again. Mix in the oats.
Divide the mixture into 9 pieces, make balls and flatten them. Place them on the baking sheet. Bake for almost 12 minutes, until the cookies change color and become firm. Let them cool for 10 minutes after you remove them from the oven.
The calorie information above is an estimate that is provided by an online nutrition calculator.