Put 1 ½ cups of the flour in the work bowl of a food processor fitted with the steel knife blade. Add the eggs, lemon zest and salt and process until the dough forms a ball. The dough should not be wet—if it is, add the remaining flour, 1 tablespoon at a time, and process the dough for about 30 seconds, or until it is smooth. Wrap the dough in plastic and let it rest for 30 minutes.
Heat the broth and keep hot on the back burner of the stove.
Put the chives and the olive oil in a blender. Whir until the oil is warm, a minute or so. Set aside with a strainer nearby.
Bring a large pot of water to a boil. Salt the water generously—Italian cooks say it should be as salty as broth.
Roll and cut the pasta into noodles:
Divide the pasta dough into eight pieces. Keep them covered with plastic so they don’t dry out. With a pasta machine or by hand, roll out and stretch each piece into a rectangle about 1/16 inch thick, using flour sparingly as needed to keep the dough from sticking to the rollers.
Cut the pasta on the noodle setting of the machine or about ¼ inch thick. Separate the strands and let the pasta dry, stretched out on towels or a pasta drying rack.
Strain the chives from the oil, discarding the pulp.
Add the lemon juice to the broth.
Drop the pasta into the boiling salted water and cook it for 30 seconds after the water returns to a boil—fresh pasta cooks very quickly and you want it to be just firm to the bite (al dente).
Drain and divide the pasta into 6 serving bowls. Pour about 1/2 cup of broth over the noodles, drizzle generously with chive oil and garnish with chive blossoms or chives. Serve immediately.