In a bowl, combine kosher salt, sugar, smoked paprika, black pepper, garlic powder, onion powder, and curing salt if using.
Rub the mixture evenly over the beef slices, coating all sides.
Transfer the beef to a sealed bag or container and refrigerate for 5 to 7 days, turning once a day so the seasoning cures evenly.
After curing, lightly rinse the beef under cold water to remove extra salt, then pat dry with paper towels.
Place the strips on a wire rack set over a baking sheet and refrigerate uncovered for 12 to 24 hours to form a pellicle (a tacky surface that helps smoky flavor adhere).
Preheat the oven to 175°C (350°F). Arrange the strips on a parchment-lined baking sheet and bake for 20 to 30 minutes, flipping halfway through, until they reach your preferred crispness.
Let cool slightly before serving or storing for later use.