  We introduce a high-order numerical scheme for fractional ordinary
differential equations with the Caputo derivative. The method is developed by
dividing the domain into a number of subintervals, and applying the quadratic
interpolation on each subinterval. The method is shown to be unconditionally
stable, and for general nonlinear equations, the uniform sharp numerical order
$3-\nu$ can be rigorously proven for sufficiently smooth solutions at all time
steps. The proof provides a general guide for proving the sharp order for
higher-order schemes in the nonlinear case. Some numerical examples are given
to validate our theoretical results.
