The Su-35 has both IRST and L band radar, the L band perhaps having the capability to see the F-35 100 miles away.
L band radars are quite common, many (most?) Air Traffic Management long-range surveillance radars (like ARSR) operate in the L band. But they have low angular and range resolution so cannot be used for a targetting solution. But they can narrow the search volume and provide cuing to a higher frequency radar which can then saturate that volume with a lot of energy to squeeze out a signal from a stealth aircraft. L band also requires large antennas for any kind of efficiency, so if put on a fighter sized platform (like the Su-35), it will be range liimited. The large apertures required also limits the ability to use active beam forming, especially on smaller platforms.