Silicon waveguides can be functionalized with an organic chi((2))-nonlinear cladding. This complements silicon photonics with the electro-optic (EO) effect originating from the cladding and enables functionalities such as pure phase modulation, parametric amplification, or THz-wave generation. Claddings based on a polymer matrix containing chromophores have been introduced, and their strong chi((2)) nonlinearity has already been used to demonstrate ultralow power consuming modulators. However, these silicon-organic hybrid (SOH) devices inherit not only the advantageous properties; these polymer claddings require an alignment procedure called poling and must be operated well below their glass transition temperature. This excludes some applications. In contrast, claddings made from organic crystals come with a different set of properties. In particular, there is no need for poling. This new class of claddings also promises stronger resilience to high temperatures, better long-term stability, and photo-chemical stability. We report on the deposition of an organic crystal cladding of N-benzyl-2-methyl-4-nitroaniline (BNA) on silicon-on-insulator (SOI) waveguides, which have a CMOS-like metal stack on top. Adhering to such an architecture, which preserves the principal advantage of using CMOS-based silicon photonic fabrication processes, permits the first demonstration of high-speed modulation at 12.5 Gbit/s in this material class, which proves the availability of the EO effect from BNA on SOI also for other applications.