What's the best time and temperature for tenderness when baking red potatoes?
It depends greatly on how hungry I am. :-)

350F for about an 60-90 minutes, depending on how many are in there.

425F for about 40-60 if I'm hungry and impatient.

Microwave on high for a few minutes (few holes poked in it with a fork) if I'm really hungry and really impatient.

They're done when a fork goes in easily.