1-First Step: Prep and mise en place
Preheat your oven to 350°F and line two baking sheets with parchment paper. Measure all ingredients precisely: spoon and level the 2 1/3 cups of all-purpose flour so the dough has the right texture. Having a small cookie scoop and a teaspoon ready will speed up the process and create evenly sized cookies.

2-Second Step: Cream butter and sugar
In a large mixing bowl, add 1 cup softened butter (2 sticks) and 2/3 cup white granulated sugar. Using a handheld or stand mixer on medium speed, cream until the mixture is pale and slightly fluffy, about 2 to 3 minutes. Properly creamed butter and sugar trap small air pockets for a light cookie crumb.

3-Third Step: Add egg yolks and flavoring
Add the 2 egg yolks one at a time, beating well between additions so each yolk is fully incorporated. Stir in 1 teaspoon vanilla extract. If you prefer, substitute the vanilla with 1 teaspoon almond extract or add a little lemon zest for a brighter finish. Mixing yolks in slowly keeps the dough smooth and avoids breaking the emulsion.

4-Fourth Step: Combine dry ingredients
Gradually add 1/2 teaspoon kosher salt and the 2 1/3 cups all-purpose flour to the bowl. Mix on low speed or fold in by hand until the dough comes together and there are no dry streaks of flour. The dough should be soft but not sticky; if it seems too wet because of warm butter, chill for 10 minutes.

5-Fifth Step: Shape the cookies
* Using a small cookie scoop, form the dough into even-sized balls and place them on the prepared baking sheets about 2 inches apart so the cookies have room to spread.
* Press your thumb or the back of a small spoon into the center of each cookie without pressing all the way through to make an indent. Aim for an indent about 1/2 inch deep so it will hold the jam while baking.

6-Sixth Step: Fill and bake
Spoon about a teaspoon of raspberry jam into each indented center. Using 1/2 cup raspberry jam total should cover the batch; if you prefer more jam, add a little extra but avoid overfilling so the jam does not run. Bake the trays for 12 to 15 minutes, rotating pans halfway through if your oven has hot spots. Cookies are done when the edges are lightly browned underneath.

7-Final Step: Cool and serve
Cool the cookies on the baking sheets for 10 minutes after removing them from the oven, then transfer to a wire rack to cool completely. Cooling on the sheet helps the cookies set so they keep their shape. Once cooled, store or serve as desired. These raspberry thumbprint cookies pair wonderfully with tea or a light dessert spread.