I suggest you go to Rotier’s on Elliston Place. Get the cheeseburger on French bread, and maybe their onion rings.
I agree with Steve’s recommendation, though I would add that you should ask for a chocolate milk shake to go with (not on the menu). Other possibilities for good burgers are Brown’s Diner and Fat Mo’s (takeout only). Bobbi’s Dairy Dip makes a good one, but I believe they are closed for the season. Though I’ve not been in several years, I have always enjoyed the burgers at Sportsman’s Grille too…