Place butter in a light-colored skillet over medium heat
Let butter melt slowly, swirling the pan occasionally
Continue cooking until butter foams, then watch for golden-brown flecks and a nutty aroma
Add sage leaves and smashed garlic (if using)
Cook for 30–45 seconds until sage is crisp
Remove pan from heat
Season with salt and black pepper
Add lemon juice or zest if using
Stir gently and use immediately