01 - Preheat the oven to 400°F (200°C) and line a baking sheet with parchment paper.
02 - Place orange and grapefruit slices in a single layer on the prepared baking sheet.
03 - Combine honey, brown sugar, vanilla extract, and cinnamon in a small bowl and drizzle evenly over the citrus slices.
04 - Bake the citrus slices for 10 to 12 minutes until lightly caramelized and aromatic; remove and allow to cool slightly.
05 - Mix pistachios, rolled oats, honey, and sea salt in a bowl. Spread on a separate baking sheet and toast in the oven for 5 to 6 minutes until golden and crisp. Let cool.
06 - Stir Greek yogurt with honey and lemon zest until smooth and creamy.
07 - Divide the yogurt into four bowls. Top each with warm roasted citrus slices and sprinkle generously with the crunchy topping.
08 - Serve immediately while the citrus slices are still warm to enjoy the optimal flavor and texture.