Blend 1 tablespoon of the butter with the dark brown sugar and gochujang in a small bowl, then leave the mixture at room temperature. The paste should look evenly red, with no separate streaks of butter.

Whisk the remaining 7 tablespoons butter with the granulated sugar, egg, salt, cinnamon, and vanilla by hand for about 1 minute. A smooth, cohesive mixture is the goal rather than a fluffy, whipped texture.

Use a flexible spatula to incorporate the baking soda, then gently work in the flour and refrigerate the bowl for 15 to 20 minutes. The chilled dough should feel less sticky while remaining soft enough to fold.

During the dough’s refrigerator rest, preheat the oven to 350 °F and cover two large sheet pans with parchment paper. The parchment should lie flat so the dough portions have an even surface beneath them.

Distribute the red paste across the chilled dough in 3 to 4 separate dollops, then draw the spatula through the bowl in broad circular sweeps. Stop with wide orange-red bands still visible against the pale dough, before the mixtures become uniformly pink.

Portion the dough with an ice cream scoop into ¼-cup mounds, leaving at least 3 inches between them and placing 4 to 5 cookies on each pan. The generous gaps give these large cookies room to spread without joining together.

Bake for 11 to 13 minutes, turning the pans halfway through, then leave the cookies on their baking sheets until completely cool. Look for lightly golden edges and dry, set centers; the cookies will settle slightly as the pans’ residual heat helps them finish setting.