Preheat oven to 300°F and line a large baking pan with parchment paper and set aside.
Cream the butter, sugar, and brown sugar together in the bowl of a stand mixer fitted with a paddle attachment on medium speed for about 2 minutes.
Add the eggs, vanilla, and lemon juice to the mixer while beating on low speed for 30 seconds, then medium speed for about 2 minutes, or until light and fluffy, scraping down bowl as needed.
In a separate medium bowl, whisk together the flour, oats, baking soda, salt, and cinnamon.
With the mixer on low speed, add the flour mixture to the butter mixture and continue mixing for about 45 seconds. Don’t overmix!
Stir in chocolate chips and walnuts by hand with a rubber spatula, do not use a mixer.
Portion dough with a large cookie scoop (about 3 tablespoons) onto the prepared baking sheet about 2 inches apart.
Bake for 20 to 23 minutes, or until edges are golden brown and center is still soft.
Remove from oven and cool on baking sheet for about 1 hour.