Whisk together oil, capers, lemon juice, salt, and pepper in a large measuring cup. I like to use a measuring cup instead of a bowl because it’s much easier to pour the dressing over the cooked beans. Set vinaigrette aside.
Bring a large saucepan of salted water to a boil; add beans and cook till tender, 3-4 minutes. Using a slotted spoon, transfer to a large bowl of ice water. This prevents the beans from continuing to cook.
Drain beans and toss with vinaigrette; adjust seasoning to taste and garnish with zest and slivered almonds.