Classic buttery shortbread thumbprint cookies made with 6 ingredients and filled with sweet and tart guava jam. Just 25 minutes from start to finish! They're great for gift giving too!
In a bowl, cream the butter and sugar together until combined then add the egg yolk, vanilla extract, and salt until smooth. Slowly add the flour and mix until no longer crumbly.
Roll into balls and place on the baking sheet. Make an indentation into each ball using a teaspoon. Be careful not to press through. Chill for 1 hour in the fridge. This is key!
Spoon jam into indentations. Use room temperature jam. Bake at 350° for 10-12 minutes or until the cookies are slightly golden brown. Let them cool for 10 minutes.