Prep the asparagus: Rinse and pat dry.
Snap off the woody ends; they’ll naturally break where the tender part begins. If the stalks are thick, peel the bottom third to keep the texture even.
Zest and juice the lemon: Zest the lemon first, then cut and juice it. Set aside 2–3 teaspoons of juice and about 1 teaspoon of zest.
Heat the pan: Place a large skillet over medium heat.
Add olive oil and butter. As the butter melts, swirl until foamy but not browned.
Add garlic (if using): Cook for 20–30 seconds, just until fragrant. Don’t let it brown, or it will taste bitter.
Sauté the asparagus: Add asparagus in a single layer.
Season with a generous pinch of salt and a few grinds of black pepper. Cook for 4–7 minutes, turning occasionally. Aim for bright green and crisp-tender.
Thin stalks cook faster; thick ones take longer.
Finish with lemon: Turn off the heat. Add the lemon juice and zest, plus a small pinch of red pepper flakes if you like. Toss to coat.
Taste and adjust salt and pepper.
Garnish and serve: Top with chopped herbs and a light shower of Parmesan, if using. Serve warm while the spears are glossy and vibrant.