Oh, I've got a whole bookshelf for this! If you want lush magic systems that actually matter to the plot AND heat, Rebecca Yarros's Empyrean series is an obvious starting point. The world-building with dragons and their riders is integral—the magic bonds directly fuel the romantic tension and conflicts. The spicy scenes are high-stakes because of that magical connection; it never feels like generic adult content dropped into a fantasy setting.
For something with a grittier, fae-oriented twist, try Sarah J. Maas's later books in the 'A Court of Thorns and Roses' saga, especially from the second one onward. The world expands into different courts with distinct magical flavors, and the romantic payoffs are, let's say, deservedly intense after all the build-up. I re-read the Winter Court scenes just for the atmosphere.
A slightly older but fantastic pick is Grace Draven's 'Radiance'. The central couple is an arranged marriage between a humanoid prince and a princess from a nocturnal, magical race. Their cultural and physical differences are a source of both tender world-building and surprisingly sensual moments. It proves you don't need constant battles for the magic to feel palpable and romantic.