Preheat your oven to 350°F (175°C) and line two baking sheets with parchment paper to prevent sticking and ensure even baking.
Toast the pecans in a dry skillet over medium heat for 5-7 minutes, stirring frequently until fragrant. This step deepens their flavor considerably. Allow to cool before chopping.
Cream together the butter and brown sugar in a large bowl until light and fluffy, about 3 minutes. The mixture should lighten in color and increase in volume.
Add the maple syrup, egg, and vanilla to the butter mixture and beat until fully incorporated and smooth. Make sure to scrape down the sides of the bowl.
In a separate bowl, whisk together the flour, baking soda, salt, and cinnamon (if using) until well combined.
Gradually add the dry ingredients to the wet ingredients, mixing on low speed just until combined. Overmixing will develop gluten and result in tough cookies.
Fold in the chopped toasted pecans by hand until evenly distributed throughout the dough.
Use a cookie scoop or tablespoon to portion the dough into 1 1/2 tablespoon balls, placing them 2 inches apart on the prepared baking sheets.
Lightly press down on each cookie with your palm or the bottom of a glass to slightly flatten them. If desired, sprinkle with a tiny pinch of flaky sea salt.
Bake for 12-15 minutes until the edges are golden brown but the centers still look slightly soft. They will firm up as they cool.
Let the cookies cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.