No ketchup, ever, seriously.
Ketchup masks flavor and that's why it is on Fast Food Burgers. When you use good meat ketchup is not desired.
Let's talk about the meat.
Whether you grill or sear do not buy grocery store hamburger. As you have read it can be anything these days and worst of all this meat has no flavor. Grass fed is best, home ground is best. A food processor can grind a blend of meats and give you a beautiful patty. Otherwise go to a good butcher and ask him to grind the cut(s) you choose. Never buy what is in the case.
Fat is key. Lean beef is death to burgers. I chose grass fed beef, that I ground with a little pork fat for extra flavor.
Make a loose patty, do not work it too much, place on a plate.
Your burger should be bigger than your bun or roll (I like Kaiser) and you need to indent it with a large spoon on both sides. Salt well and give it a grind of pepper if you like.
I like onion so I saute an onion in a separate skillet to soften.
I used a smoking hot cast iron skillet, I put a touch of sunflower oil on the burger with my finger and tossed it into the pan.
Now leave it alone. Never smash or play, you can watch but don't turn. You want a good strong sear on the burger, give it a few minutes while you make your sauce.
This is the best burger sauce ever, it makes the beef beefier and does not mask the flavor.
Great add ins include chopped chive or green onion and capers. Stir to mix, slice your bun and begin to layer the burger.
After at least 4 minutes you can lift the edge of the burger with a spatula, if it sticks it is not ready to turn, focus on your condiments.
I build my burger with sauce on both sides, onions on the bottom, then chopped lettuce, tomato and ultimately the beef.
I go for Rare to Medium, I consider well done the death of the burger.
When ready to turn, it needs only a scant time before it is done.
Do the finger test, soft is rare, slightly firm is medium rare to medium, and firm is well done. A hard burger is overcooked.
This is my completed sandwich.
Make this sauce for your next burger event, choosing and grinding meat carefully and get back to me with your reaction.