Forgive me for being a little skeptical but can you show us a screenshot of the "toast shape" done in Adobe Illustrator (showing the guide lines, please)? (I'm changing the challenge a bit because just dragging the top line isn't the same as bestowing the top corners with guides and this challenge now necessitates the guides):
And make sure to tell us how long it took you. In SVG Path Builder the toast shape above took me 10 seconds, and it never gave me grief by trying to curve the sides, while still giving me the guides for each of the relevant corner nodes. Drawing that in Inkscape is just as easy. Same for CorelDraw.
If you can manipulate the guides of your corner nodes and have them affect only the top side, then you've succeeded in making those two top corner nodes cusp. I have never seen anyone online showing cusp nodes in Illustrator.