I get the confusion because BookTok is kind of chaotic, but I don't completely agree with what the other comments are saying. Sure, there's a lot of hype and pretty covers, but that doesn't mean the books that blow up there are garbage. Sometimes they're genuinely good and the algorithm is just doing its job amplifying them. The thing is you do need to filter a bit, yeah, but don't write off everything viral.
Some Spanish authors floating around are names like Elísabet Benavent (which they already mentioned), Megan Maxwell if we count the one who writes in Spanish and lives here, and there are other more recent ones gaining traction on social media. But honestly BookTok shifts so much that every couple months there are new favorites, so you're better off searching directly on the platform for what's trending in the Spanish-speaking community and reading the comments on posts. That way you get a sense of whether people are talking about the plot or just the aesthetics 📚
My advice: start with something that catches your eye visually (because yeah, let's be real) but before you buy it check the reviews on Goodreads or in the TikTok comments themselves. Users often leave clues about whether the book has substance or if it's just a pretty cover. And don't be embarrassed if you end up reading something that's trendy, it might actually be genuinely entertaining.