To toast pecans: spread 1 cup chopped pecans, on an ungreased sheet pan and bake at 350°F degrees for 6-8 minutes. Cool and store if not using right away.
Place butter in a small skillet over medium heat. Once 1 cup unsalted butter is melted, gently swirl the butter in the pan while it cooks until the butter reaches a light amber color. Remove from heat once it reaches an amber color – do not overcook. Allow to cool slightly.
Sift or whisk the 3 cups all-purpose flour, 1 teaspoon cream of tartar, 1/4 teaspoon salt and 1 teaspoon baking soda in a medium sized bowl.
In a large mixing bowl, combine the 2 cups light brown sugar, and slightly cooled browned butter. Mix well and add the 2 large eggs, and 1 teaspoon vanilla extract.
Add in sifted dry ingredients, followed by 1/2 cup of the toasted pecans. Form dough into logs about 2 inches in diameter; coat logs in remaining chopped pecans.
Wrap logs of dough in either plastic wrap or parchment paper. Refrigerate overnight (or freeze if not planning to bake right away).
Slice dough 1/4" thick; place on lined baking sheet and bake @375°F 10-12 minutes* Cool on wire rack.
Notes
The toasted pecans can be done in advance
To store in refrigerator: store dough logs up to 7 days
To store in freezer: store dough logs for up to 3 months. Add 2 minutes to the baking time if baking from a frozen state.
Baked cookies: store at room temperature up to 3 days in an airtight container; store baked cookies in freezer up to 45 days in an airtight container