Step 1

Preheat the oven to 450 F. Peel, halve, and seed butternut squash and cut crosswise into ¼-inch thick slices. Peel onion and cut through the root into 1-inch wedges.

Step 2

Heat oil in a medium-sized, nonstick ovenproof skillet over medium-high. Working in batches, cook squash and onion wedges in a single layer, flipping once, until golden brown and crisp-tender (a knife should slip in and out with a little resistance), 3 to 5 minutes. Transfer to a plate.

Step 3

Reduce heat to medium-low. In a large bowl, whisk together eggs, lemon zest, salt and pepper; stir in spinach. Add the egg mixture to the skillet. Cook, stirring, until large curds form and the edges just begin to set, about 1 minute. Remove from the heat. Nestle the squash and onions into the egg mixture, then dollop the cheese spread over the top. Transfer to the oven and cook until the eggs are set and the top is browned in places, about 10 minutes. Let stand for at least 10 minutes before serving.