Bring a large pot of salted water to a boil and prepare a bowl of ice water for blanching.
Add the green beans to the boiling water and cook for 3-4 minutes until crisp-tender and bright green, then immediately transfer to the ice water to stop the cooking.
In a dry skillet over medium heat, toast the sliced almonds for 3-4 minutes, stirring frequently until golden brown, then remove from the skillet and set aside.
In the same skillet, melt the butter over medium heat and continue cooking, swirling the pan occasionally, until it turns golden brown and smells nutty, about 3-4 minutes.
Add the minced garlic to the brown butter and cook for 30 seconds until fragrant.
Drain the green beans thoroughly and add them to the skillet along with the toasted almonds, tossing to coat everything in the brown butter.
Add the lemon juice and lemon zest, season with salt and pepper, toss once more, and serve immediately.