Step 1

Heat air fryer to 400°. Toss brussels sprouts with 2 Tbsp. oil in a large bowl to coat. Season with salt.

Step 2

Transfer brussels sprouts to air fryer and cook, shaking halfway through, until crispy and golden brown, 7–9 minutes.

Step 3

Meanwhile, heat remaining 2 tsp. oil in a small saucepan over medium. Add ginger and turmeric and cook, stirring, until fragrant and ginger is slightly softened, about 1 minute. Add honey, butter, red pepper flakes (add more for extra heat), and 1 tsp. Diamond Crystal or ½ tsp. Morton kosher salt and whisk until emulsified, about 1 minute. Increase heat to medium-high, whisk in lemon juice (mixture will bubble up quite a bit, then settle). Cook, whisking constantly, until thickened enough to coat the back of a spoon, about 2 minutes. Remove sauce from heat.

Step 4

Transfer brussels sprouts to a platter and drizzle sauce over.Do ahead: Sauce can be made 2 days ahead. Let cool. Transfer to an airtight container; cover and chill. Reheat with 2 Tbsp. water in a medium skillet over medium, whisking until emulsified.