Cauliflower Eggs Benedict with Turmeric Yogurt Sauce

Preheat oven to 425°F. Line a large rimmed baking sheet with parchment paper. 

Using a sharp knife, cut cauliflower into four 1/2-inch-thick steaks, making sure each steak includes part of the core to help it stay together; reserve any florets and extra cauliflower for another use. Brush both sides of the cauliflower with 2 tablespoons oil and season with 1/4 teaspoon salt. Arrange on the prepared baking sheet. Roast until crisp and deeply golden, about 25 minutes. 

Meanwhile, heat the remaining 2 tablespoons oil in a large skillet over medium heat. Add garlic and cook, stirring, until fragrant, about 1 minute. Add chard and cook, stirring, until wilted, 2 to 3 minutes. Stir in 1/4 teaspoon salt and lemon zest. Transfer to a bowl and cover to keep warm. Rinse and dry the skillet.

Place butter in a medium microwave-safe bowl and microwave on High until melted, 15 to 20 seconds. Whisk in turmeric and the remaining 1/8 teaspoon salt, then yogurt, lemon juice and 1/2 teaspoon vinegar.

Add 1 1/2 inches water and the remaining 1/2 teaspoon vinegar to the skillet. Bring to a boil. Reduce the heat to a low simmer. One by one, crack eggs into a small bowl and carefully transfer to the simmering water; cook until the whites are opaque and cover the yolks, about 3 minutes. With a slotted spoon, transfer the poached eggs to a towel-lined plate. 

Arrange a cauliflower steak on each of 4 plates. Top each with about 1/3 cup chard, then top with an egg and about 1/4 cup hollandaise.