We have always said to our daughter, even as a baby, 'you're frustrated, we understand, but we will help you'.
Well that's not ignoring her then, is it?

As I said, tantrums are not always frustration - it could be tiredness, hunger, thirst - and I would rather deal with the issue straight away, and help them learn to deal with it straight away than put us through more stress than we need be. Especially is it's through hunger or whatever, I would rather not make her wait. I would also say that ignoring a child is not gentle parenting, but that's just me.