A method is provided for heating a furnace arranged with a heating zone heated with a burner providing a flame extending in a longitudinal direction and fed with a fuel and a primary oxidant, the burner is operated with a mass relationship between the fed fuel and primary oxidant permitting less than 50% of the fed fuel to be combusted using the primary oxidant, and a respective pair of secondary oxidant lances are provided one either side of the furnace pointing into the heating zone, lancing a secondary oxidant into the heating zone downstream of the burner substantially parallel with a cross plane, such that a temperature is measured downstream of the lances and that each of the lance pairs includes an upstream, low-speed first and a downstream, high-speed second lance, wherein the amount of secondary oxidant supplied via the first lance is regulated to achieve a homogenous lateral temperature profile. A related furnace is also provided.