  We present a general approach to sparse domination based on single-scale
$L^p$-improving as a key property. The results are formulated in the setting of
metric spaces of homogeneous type and avoid completely the use of
dyadic-probabilistic techniques as well as of Christ-Hyt\"onen-Kairema cubes.
Among the applications of our general principle, we recover sparse domination
of Dini-continuous Calder\'on-Zygmund kernels on spaces of homogeneous type, we
prove a family of sparse bounds for maximal functions associated to
convolutions with measures exhibiting Fourier decay, and we deduce sparse
estimates for Radon transforms along polynomial submanifolds of $\mathbb R^n$.
