A cooktop appliance includes a gas burner assembly positioned on a panel of the cooktop appliance and a grate that suspends the burner in air above the panel. The gas burner assembly includes an inwardly directed burner that provides more uniform heating of a cooking utensil supported on the grate. In addition, a large aperture extends through the center of the burner to ensure proper delivery of air to mix with fuel for combustion. The resulting cooktop appliance provides improved heating over the entire cooking utensil and simplifies the cleaning process.