Prepare the Pan Line a quarter sheet pan with a sheet of parchment paper, ensuring it lays flat against the bottom and sides to prevent sticking.
Toast the Nuts Preheat your oven to 325°F (165°C). Spread the unsalted pistachios on a small baking tray and toast for 5–7 minutes until fragrant. Let them cool completely, then roughly chop.
Whip the Yogurt Base In a medium bowl, combine the non-fat Greek yogurt, agave nectar, lime zest, vanilla extract, and ground cardamom. Stir vigorously with a spatula until the mixture is smooth, creamy, and the spices are evenly distributed.
Assemble the Bark Pour the yogurt mixture onto the prepared sheet pan. Use the spatula to spread it into a thin, even layer, approximately ¼-inch (⅔ cm) thick.
Create the Swirl Drop small dollops of the strawberry-rhubarb preserves randomly over the yogurt layer. Drag the tip of a skewer or a spoon through the dollops to create an elegant, marbled pattern.
Add the Crunch Evenly sprinkle the chopped, toasted pistachios over the entire surface of the swirled yogurt.
Freeze Until Firm Carefully transfer the pan to the freezer. Let it freeze for at least 2 hours and 30 minutes, or until the bark is completely solid and firm to the touch.
Portion and Serve Once frozen, lift the parchment paper to remove the bark from the pan. Break it apart into 24 rustic pieces. Serve immediately.