In a medium saucepan, melt the butter over medium heat, swirling and stirring occasionally until it turns a golden brown color and releases a nutty aroma (5-7 minutes). Pour into a standing mixer bowl or large heat safe bowl. Set aside to cool.

In a medium bowl, whisk together the flour, cream of tartar, baking soda, cinnamon, ginger, allspice, cloves, nutmeg, cardamom, and salt. Set aside.

Once the brown butter is cooled (about 20 - 30 minutes), beat the butter with the granulated sugar, brown sugar, and molasses with a paddle attachment until well combined. Alternatively, you can use a handheld mixer or whisk.

Add the egg and egg yolk, one at a time, beating until fully incorporated, followed by the vanilla extract. Cream together for 3-4 minutes.

Take the bowl off the standing mixer, and add the dry ingredients to the wet ingredients and fold with a spatula or wooden spoon by hand, mixing until just combined.

Wrap the dough in saran wrap and chill in the fridge for at least an hour, up to overnight.

Remove from the fridge and roll into balls (about 1 ½ inches wide).

Preheat the oven to 350 F and place the rack in the center of the oven. Line two baking trays with parchment paper.

In a bowl, combine the sugar coating ingredients. Roll each ball to coat in the spiced sugar.

Place on the baking tray and bake one tray at a time for 8 to 11 minutes. It will be difficult to tell doneness by color due to the molasses, but you can tell they’re done when they look slightly raw in the center but have formed a thin crusty edge on the outside.

Optionally, sprinkle them with flaky salt right when they’re done cooking.

Let them cool for at least 5 minutes, then move them to a wire rack to finish cooling.