Arrange the swordfish steaks in a nonreactive baking dish.
Season on both sides with lemon juice and salt and pepper.
Drizzle with olive oil.
Turn the steaks a few times to coat and marinate in the refrigerator for 30 minutes.
Meanwhile, make the salsa verde: Place the garlic, parsley, lemon zest and juice, capers and fish sauce or anchovy, if using, in a food processor and finely chop.
Work in the hot red pepper flakes and olive oil.
Add salt (sparingly) and pepper to taste - the salsa should be highly seasoned—place in a serving bowl.
Meanwhile, build a fire in your KUDU Grill with a hot zone for searing and a medium zone for cooking.
Brush and oil the grill grate.
Arrange the swordfish steaks over the hot fire and grill until the fish is browned, sizzling, and cooked through 4 to 6 minutes per side, 8 to 12 minutes in all.
Move the steaks to the medium zone if they start to burn.
Transfer to plates or a platter.
Serve the swordfish steaks with the salsa verde on the side for spooning over the fish.
Add the grilled lemons to the plates or platter for squeezing.
Enjoy!