Put sour cream and lemon juice in a small bowl and set aside.
In a food processor, add flour, salt, and sugar. Whirl for a few seconds to mix.
Add cold butter to the flour mixture and pulse until butter is incorporated into the flour, about 15 seconds.
Add ice water to sour cream and lemon juice. Whisk together. Add to the food processor and pulse until it forms a crumbly dough. Add a couple drops more if the dough is too dry.
Shape the dough into a disc, wrap in plastic wrap, and refrigerate for 30~ 45 minutes.
Preheat oven to 375.
Roll out the disc, about 1/8", and use a cookie cutter to cut out the hearts.
Put the dough hearts onto a parchment-lined baking sheets and chill for 15 minutes.