Tunable　optical　material　properties　enable　novel　applications　in　both　versatile　metamaterials　and　photonic　components　including　optical　sources　and　modulators.　Transparent　conductive　oxides　(TCOs)　are　able　to　highly　tune　their　optical　properties　with　applied　bias　via　altering　their　free　carrier　concentration　and　hence　plasma　dispersion.　The　TCO　material　indium　tin　oxide　(ITO)　exhibits　unity-strong　index　change　and　epsilon-near-zero　behavior.　However,　with　such　tuning　the　corresponding　high　optical　losses,　originating　from　the　fundamental　Kramers-Kronig　relations,　result　in　low　cavity　finesse.　However,　achieving　efficient　tuning　in　ITO-cavities　without　using　light-matter　interaction　enhancement　techniques　such　as　polaritonic　modes,　which　are　inherently　lossy,　is　a　challenge.　Here　we　discuss　a　novel　one-dimensional　photonic　crystal　nanobeam　cavity　to　deliver　a　cavity　system　offering　a　wide　range　of　resonance　tuning　range,　while　preserving　physical　compact　footprints.　We　show　that　a　vertical　silicon-slot　waveguide　incorporating　an　actively　gated-ITO　layer　delivers　similar　to　3.4　nm　of　tuning.　By　deploying　distributed　feedback,　we　are　able　to　keep　the　Q-factor　moderately　high　with　tuning.　Combining　this　with　the　sub-diffraction　limited　mode　volume　(0.1　(lambda/2n)(3))　from　the　photonic　(non-plasmonic)　slot　waveguide,　facilitates　a　high　Purcell　factor　exceeding　1000.　This　strong　light-matter-interaction　shows　that　reducing　the　mode　volume　of　a　cavity　outweighs　reducing　the　losses　in　diffraction　limited　modal　cavities　such　as　those　from　bulk　Si3N4.　These　tunable　cavities　enable　future　modulators　and　optical　sources　such　as　tunable　lasers.