We prove almost everywhere convergence of continuous-time quadratic averages with respect to two commuting
$\mathbb {R}$-actions, coming from a single jointly measurable measure-preserving
$\mathbb {R}^2$-action on a probability space. The key ingredient of the proof comes from recent work on multilinear singular integrals; more specifically, from the study of a curved model for the triangular Hilbert transform.