Preheat the oven to 425°F (220°C).

In a large bowl combine 4 cups cauliflower florets, 2 large tomatoes (quartered), and 1 medium red onion (roughly chopped). Add 2 tablespoons melted coconut oil and 1 1/2 teaspoons yellow curry powder. Season with sea salt and freshly ground black pepper to taste and toss until the vegetables are evenly coated. Spread the vegetables in one layer on a large rimmed baking sheet.

In a small food processor combine the remaining curry powder (2 teaspoons), 2/3 cup roasted salted cashews, and a pinch of salt and pepper. Pulse until the cashews are broken down but still have some small chunks for texture. Transfer the crushed cashew mixture to a shallow plate.

Pat 1 pound boneless skinless chicken breasts dry with paper towels. Pour 1 large egg white onto another shallow plate.

Working one breast at a time, dredge a chicken breast in the egg white, letting any excess drip off, then press both sides into the crushed cashews so the cashews adhere. Repeat with the remaining breasts.

Place a small cooling rack with legs (that fits on your sheet pan) on top of the sheet pan over the vegetables. Arrange the cashew-coated chicken breasts on the rack so air can circulate around them.

Bake in the preheated oven until the chicken reaches an internal temperature of 165°F (74°C) at the thickest part, about 14–15 minutes depending on thickness. Use an instant-read thermometer to confirm doneness.

Remove the sheet pan from the oven and let the chicken rest on the rack for 3–5 minutes. Scatter 2 cups thinly sliced cucumber (sliced and halved) over the roasted vegetables, then garnish with chopped fresh mint and chopped fresh cilantro. Adjust salt and pepper to taste.

Serve warm directly from the pan or transfer to a platter.