Preheat oven to 400°F (200°C) and line a baking sheet with parchment paper.
Toss the butternut squash cubes with 1 tablespoon of olive oil, 1/2 teaspoon salt, and 1/4 teaspoon pepper. Spread in a single layer on the baking sheet.
Roast the squash for 20 to 25 minutes until tender and slightly caramelized at the edges.
While squash roasts, season steak cubes with remaining salt and pepper.
Heat remaining olive oil in a large cast-iron skillet over medium-high heat. Add steak cubes in a single layer and sear for 2 to 3 minutes without moving to develop a crust.
Flip steak cubes and cook for an additional 2 minutes.
Lower heat to medium and add butter, minced garlic, rosemary, and thyme to the skillet. Tilt the pan and spoon the melting herb butter over the steak for 2 minutes.
Divide cooked quinoa and baby spinach among four bowls.
Top each bowl with roasted butternut squash and the garlic herb steak cubes, drizzling any remaining butter from the pan over the top.