Bring a 6- to 7-quart pot of water to a boil. Add the beans and cook until bright green and barely crisp-tender, about 2 minutes. Drain in a colander and rinse under cold running water until completely cool. Spread the beans on a clean kitchen towel and dry thoroughly.
In a 12-inch skillet, heat the butter and oil over medium-low heat until the butter melts and the foam subsides. Add the almonds and cook, stirring occasionally, until golden-brown all over, about 3 minutes.
Using a slotted spoon, transfer the almonds to a plate. Reduce the heat to low and add the garlic to the skillet. Cook, stirring constantly, until fragrant, about 30 seconds. Add the beans, increase the heat to medium, and cook, tossing occasionally, until crisp-tender and lightly browned in some places, 5 to 8 minutes.
Stir in the lemon juice and season to taste with salt and pepper. Transfer to a serving platter, sprinkle with the almonds, and serve.
The beans can be blanched (boiled until barely crisp-tender) up to 1 day ahead; refrigerate wrapped in paper towels in a plastic bag.