Bring a large pot of salted water to a boil. Add broccoli rabe and blanch for 3 minutes until bright green but still firm. Drain and immediately plunge into an ice bath to stop cooking. Squeeze out excess water thoroughly — this is crucial, as too much water will make the pesto watery.
In a food processor, pulse garlic, cheese, and nuts until coarsely chopped. Add broccoli rabe and process until combined but not completely smooth. With the motor running, slowly drizzle in olive oil. Season with lemon juice, red pepper flakes, salt, and pepper to taste. Set aside (you'll have extra — great for other uses).
If your coppa is already pressed (vacuum-sealed or deli-sliced), skip ahead. Otherwise, wrap 6-8 ounces of regular coppa in parchment paper, then place between two sheets of plastic wrap. Set a heavy skillet on top and add something weighted — a cast iron pan filled with cans works perfectly. Press for at least 2 hours, or preferably overnight.
Unwrap the pressed coppa and slice as thin as possible against the grain.
Brush bread slices lightly with olive oil on one side. Toast in a skillet over medium heat until golden brown.
Layer each toast with sliced coppa, fresh basil leaves, and a generous spoonful of pesto. Serve immediately at room temperature for the best texture, or warm gently before serving.
