We were fortunate that we can gate off the playroom that the kitchen overlooks, so I can basically keep the baby out of the kitchen when cooking. But as DS was allowed out more (lol - sounds terrible) he has learned about hot things by actually touching them.. ok.. not when blasting hot.. but he's felt hot drinks, and a warm oven door. He's been taught that it's very hot, and he's never touched it. From very early on (using baby signs) he's walked past fires and ovens and told us they're hot. He still needs reminding, but I usually put the oven light on when it's hot so he knows when it's hot.

That oven guard looks good if you're worried about it.