Preheat oven to 375°F (190°C). Line baking sheets with parchment paper.
Cream the butter (1/2 cup) and cream cheese (4 ounces) together in a large mixing bowl with a hand mixer on medium speed for 2–3 minutes, until smooth, fluffy, and lightened in color.
Add the powdered sugar (1 1/2 cups) gradually and beat until creamy and well combined. Scrape the bowl as needed.
Mix in the egg (1) and vanilla (2 teaspoons) until fully incorporated and smooth.
In a separate bowl, whisk together the flour (1 3/4 cups), baking powder (1 teaspoon), cream of tartar (1/4 teaspoon), and salt (1/2 teaspoon) until evenly combined.
Add the dry ingredients to the creamed mixture and stir gently with a wooden spoon or spatula just until no streaks of flour remain. Avoid overmixing.
Chill the dough for at least 30 minutes (or up to 24 hours).
In a small bowl, combine granulated sugar (1/2 cup) and cinnamon (1 tablespoon) for rolling.
Scoop the chilled dough into 1 ½-tablespoons balls using a cookie scoop. Roll each ball in the cinnamon-sugar mixture to coat.
Place on the prepared baking sheet about 2 inches apart and gently press each cookie slightly to flatten the top.
Bake for 10–12 minutes, or until the edges are just barely golden and the centers look soft but set.
Cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.