“…Even in the case of tensor-product domains, where tensor-product orthogonal expansions can be used (see, e.g., [24,42]), hyperinterpolation is intrinsically nontensorial and thus generates nontensorial cubature formulas. As known, there are also other ways of constructing useful nontensorial cubature formulas, like the so-called sparse grids introduced by Smolyak in the '60s (cf., e.g., [40,7,28,30,31] and references therein). In the present bidimensional context numerical tests and comparisons with available implementations (like, e.g., [8]), have shown that nontensorial formulas generated via (hyper)interpolation seem more effective.…”