Thanks to the many great ideas and photos on this site, I was able to pull off the best Homemade Fancy Tea Party Teapot Cake I've ever made for my daughter's 5th birthday! I bought 2 strawberry cake mixes, baked one in a (10 cup) Pyrex bowl and the other in a regular 13x9 cake pan. After Googling "Baking Pyrex bowl cake" I very generously greased/floured the bowl and baked the cake 25 degrees less than the instructions on the box for an hour...checked with a knife and ended up adding about 20 more minutes. It puffed up a lot in the oven but the dome mostly collapsed while cooling.
I let it cool, ran a knife around the outside and then put a plate on top and carefully flipped it - came out beautifully. Froze it for a bit, then trimmed the dome flat, put it on top of the sheet cake and "traced" the circle out (I used the 13x9 pan because that was almost exactly the exact additional height I wanted). Put both in the freezer for a couple hours and then crumb-coated and froze overnight. The next day I layered the cakes with frosting in between and frosted with a 1.5 cans of storebought frosting.
Used fondant for the knob, spout and handle and attached the latter 2 with 2 half-skewers each. The handle stayed great but the spout started falling out after a couple hours (I think it also might have looked better if I flipped it upside down. Just stuck the knob and flowers on with frosting and decorated with Betty Crocker cupcake icing (which comes with decorating tips)...didn't make a separate lid just used the icing to "draw" the outline.
My daughter LOVED her cake and it got a ton of compliments. Thanks for all the great ideas on this site!