symmetric monoidal (∞,1)-category of spectra
The notion of Cartesian fibration of dendroidal sets is the generalization from simplicial sets to dendroidal sets of the notion of Cartesian fibration. Accordingly, it is models the notion of Grothendieck fibration for (∞,1)-operads. Its 1-operadic analog is the notion of fibration of multicategories.
This is (Heuts, theorem 0.1).