• vegetable oil
• ¹⁄₂ cup (64 g) onion (optional), finely diced

Heat oil in a large skillet over medium heat until hot and shimmering but not smoking; add onion and cook, stirring occasionally, until softened, about 4 minutes.

• 1 Tbsp, 1 ¹⁄₂ tsp taco seasoning

Add spice packet; cook, stirring constantly, until fragrant, about 1 minute.

• 8 oz (230 g) ground beef

Add ground beef and cook, stirring often, until it is no longer pink, about 5 minutes. (Note: you may need to use a spatula to break up the block of meat into smaller pieces before you can stir frequently.)

• ¹⁄₄ cup crushed tomatoes (optional) or tomato sauce (optional)
• ¹⁄₄ cup (59 g) water
• 1 tsp white balsamic vinegar (optional) or apple cider vinegar (optional)

Add tomatoes or tomato sauce, water, and vinegar; bring to simmer.

• kosher salt, to taste

Reduce heat to medium-low and simmer, uncovered, stirring frequently, until liquid has reduced and thickened (mixture should not be completely dry), about 10 minutes. Taste, adjust seasonings with salt.

• flour tortilla, for serving

If using hard tortilla shells, you can toast them in the oven or toaster oven at 350ºF for about 2 minutes. If using flour tortillas, wrap the tortillas in foil, and place in a 350ºF oven for 15 minutes or until warm. Sometimes I just toast them in the toaster. Remove from oven, and transfer to tea towel to keep warm.