2. In a large skillet or frying pan, heat the olive oil or butter over medium-high heat until it shimmers. Add the thinly sliced onions to the hot skillet and saute for about 5 minutes. Add ½ cup water to the pan and continue to stir. When all the water has evaporated, add in the baking soda water and continue to stir constantly. The baking soda will help speed up the caramelization process.