Use a torch. I don't think your heat source is adequate for a good result, I use an Iwatani chef's torch, around $25 on Amazon. Keep the torch moving, but be bold. I get excellent results and it is fairly quick. Sometimes I use it in combination with a big Creuset skillet on the electric range with a bit of bacon fat in the pan. Don't worry about the occasional flames. The combo allows the cration of beautiful even results on roasts whereas the skillet alone would give an uneven sear.