Gently tear the Boston lettuce into bite-sized pieces. If the arugula leaves are large, tear them in half.
Place all the prepared greens into a large salad bowl.
Drizzle the olive oil over the greens and toss gently until every leaf is lightly coated. This helps protect the leaves from the acidity of the lemon juice.
Sprinkle the lemon juice over the salad and toss again to combine.
Add the grated Parmesan cheese, a pinch of salt, and a few grinds of fresh black pepper. Give the salad one final toss.
Serve immediately for the best texture and flavor.
Adjust the dressing to your taste. The size of lettuce heads and arugula bunches can vary, so feel free to add a little more or less oil and lemon juice.