Set a steamer basket in a saucepan with 4-5 cm of simmering water. Add the broccoli. Cover and reduce heat to medium and let cook until the broccoli is tender; about 5-6 minutes. (I test this by checking if the broccoli can be pierced with a fork). As soon as it is tender, remove from the heat and place in serving bowl.
Drizzle with the pistachio oil and lemon juice, season with salt and pepper and gently toss. Sprinkle with the chopped pistachios and serve.