Why You Should Not Sear Meat with Onions
The best way to sear meat for stews is to brown it on its own, without onions. Onions are roughly 90% water, and that water drops the temperature of the pot — so instead of searing, the meat ends up steaming.
Two things matter before searing: first, pat the meat completely dry with a paper towel, because browning (the Maillard reaction) cannot even begin until the surface moisture has evaporated. Second, cut the pieces to roughly the same size so they all finish searing at the same time.
Pour a small amount of oil into the pot or pan and let it get properly hot — hot enough that the oil shimmers, around 180–190 °C. Arrange the meat pieces with space between them, and most importantly: do not crowd the pan. If there is a lot of meat, sear it in two or three batches, because too much meat at once suddenly drops the pan temperature and everything releases its juices. Once the meat is in, leave it untouched until one side is fully browned (about 2–3 minutes depending on thickness), then turn it and brown the other side the same way.