In a small bowl, stir together 1 tablespoon butter, the brown sugar and gochujang until smooth. Set aside for later, at room temperature.

In a large bowl, by hand, whisk together the remaining 7 tablespoons butter, granulated sugar, egg, salt, cinnamon and vanilla until smooth. Switch to a flexible spatula and stir in the baking soda. Add the flour and gently stir to combine. Place in the refrigerator until less sticky, about 15 to 20 minutes.

While the dough chills, heat the oven to 350 degrees and line 2 large sheet pans with parchment.

Remove the dough from the refrigerator. Spoon the gochujang mixture over the cookie dough in 3 to 4 blobs. Gently swirl the gochujang mixture into the dough to create orange-red streaks.

Use an ice cream scoop to drop out ¼-cup rounds, spaced 3 inches apart on the sheet pans (about 4 to 5 cookies per pan). Bake until lightly golden at the edges, 11 to 13 minutes. Let cool completely on the pan; the cookies will flatten slightly as they cool.