Yes, you can garnish a crème brulee without a torch.  Preheat the broiler of your oven.  Add a thin, even layer of sugar to the top of the custard and then place under the broiler to brown the sugar.  Rotate the ramekin under the broiler when needed. Using an air fryer in a pinch has even worked for us.  Sprinkle a thin layer of sugar on top of the custard and place the whole ramekin into the air fryer basket.  Set the heat to 400° and air fry for several minutes until a burnt cream forms.