Preheat the oven to 350F (177C). Line a baking sheet with parchment paper.
In a bowl or stand mixer, add the softened butter and sugar. With the paddle attachment on the mixer, or using a hand mixer, beat the sugar and butter together until smooth.
Add the eggs and vanilla and beat until fully incorporated.
In a separate bowl, combine the flour and baking powder with a spoon or whisk. Sift the dry ingredients gradually.
You should have a sticky dough that holds its shape. If needed, switch to a rubber spatula or use your hands.
Stir the diced apples into the cookie dough and mix until incorporated. (I like to use my hands for this part.)
Use a large cookie scoop to scoop up the batter. Even out the bottom of the cookies by pressing the scoop against the sides of the bowl. Then transfer the leveled out scoops of dough to the baking sheet. (Our batter made 14 big cookies but you can make them as small or as big as you like.)
Bake for 20-25 minutes. Let cool, then enjoy warm!
Video
Notes
Don't Sweat It: When my mom was first developing this recipe, she would put all the ingredients in a bowl at once (besides the apples), and the cookies came out great every time. This recipe is very forgiving, so don't worry too much about perfecting the method.
Pour Some Sugar on These: I love the taste and appearance of fresh baked goods dusted in powdered sugar (aka confectioners sugar, aka icing sugar). It's optional but recommended in this recipe. You can make your own powdered sugar by blending cane sugar in a blender or food processor until powdered.
Check Your Baking Powder: Always check the expiration date on your baking powder. You can also test if it's still good by adding some to warm water. It should fizz up right away.
Bake with Measurements: To translate the cup amounts to grams, underneath the ingredient list, select "Metric."