A burner assembly for a cooktop comprises a spreader comprising (i) a central portion through which an axis extends, the central portion with a bottom surface, (ii) a plurality of apertures through the spreader, the plurality of apertures disposed further away from the axis than the central portion, and (iii) a ridge projecting from the bottom surface, the ridge disposed further from the axis than the central portion but closer to the axis than the plurality of apertures.