Add beef, breaking it up with a spoon while stirring. Season with salt, pepper and chile de árbol, if using. Sear until beef browns in spots, about 6 minutes. Add spinach and stir until wilted.

In a large bowl, whisk together the oil, spice mixture, 2 teaspoons salt, 1 teaspoon pepper, and the chile de árbol until well blended. Add the calabaza and toss until the oil-spice mixture coats ...