Let's focus in a little on that flame:
It could be sharper, but, you know, for the sake of argument. Now, in that form, the Rude Pundit glanced at it and thought, "Huh. That looks familiar. Like the symbol for natural gas." It was time for a few precious seconds on the Google machine.
Here's one of the flame symbols for natural gas:
And for the sake of comparison, here's Cruz's flame with the color taken down a great deal (and, no, the Rude Pundit is no Photoshop expert):
Of course, it could be a coincidence. You know, there are many three-curve symbols for fire. But most are certainly different enough not to be confused.
Perhaps the truth here is that Cruz wants you to associate him with natural gas, a kind of pro-fossil fuel statement. Or maybe it's all unintentional and we should just laugh at gasbag Cruz and this ironic karmic comeuppance.
But it is definitely just on the other side of "curious."