Yes, this is gluten free
A single-ingredient food that grew, swam or walked contains exactly what it is. Water, salt, tomatoes, chicken, almonds and eggs have no gluten and never have had. This is a statement about the food itself and nothing else — the moment something is breaded, marinated, dusted to stop it sticking, or cooked in a kitchen that also makes bread, the answer comes from that process rather than from the ingredient.
buttermilk is covered by CiCi's entry on whole foods, which share this answer and the reasoning behind it.
Every one of these is the same ingredient. The number of names is a large part of why gluten slips past people who read every label.
Point CiCi at the barcode on the product you're holding and get this same reasoning in about two seconds, plus the carbs and the full nutrition panel. 360,000+ packaged foods are already read and waiting.
This answer comes from CiCi's ingredient lexicon — the same rules the scanner uses, not a separate article. Where reputable sources disagree, CiCi takes the conservative position and says so.