#circle[
  #set align(center + horizon)
  Automatically \
  sized to fit.
]

#import "@preview/cetz:0.3.1": canvas, draw, tree

#set page(width: auto, height: auto, margin: .5cm)

#canvas(
  length: 1cm,
  {
    import draw: *

    circle((0, 0))
    content((), [Circle that fits the content])
    circle((0, 0), radius: auto)
    content((), [Circle that fits the content])
    circle((0, 3), radius: (auto, auto))
    content((), [Ellipse that fits the content])
  },
)