The rapid evolution of electric vehicles (EVs) has amplified the demand for highly integrated, efficient, and intelligent powertrain architectures. In the current automotive landscape, EV powertrain systems are often composed of discrete ECUs such as the OBC, MCU, DC-DC Converter, PDU, and VCU, each operating in isolation. This fragmented approach adds wiring harness complexity, control latency, system inefficiency, and inflates costs making it harder for OEMs to scale operations, lower expenses, and accelerate time-to-market. This paper addresses the core issue of fragmented control architectures in EV powertrains by proposing an integrated domain controller-based solution for EV powertrain. The technical gap lies in the absence of a centralized intelligence capable of seamlessly managing and synchronizing the five key powertrain aggregates: OBC, MCU, DC-DC, PDU, and VCU under a unified software and hardware platform. This fragmentation leads to redundancy in computation, increased BOM cost, and challenges in system diagnostics, leading to sub-optimal vehicle performance. The objective of this work is to develop and validate an Integrated EV Powertrain System using a centralized Domain Controller (DC) that consolidates the control of all five aggregates. The architecture leverages wide bandgap (WBG) semiconductor devices such as SiC MOSFETs which enables high-efficiency, high-frequency operation across the power stages with reduced thermal losses. The goal is to improve efficiency, reduce system complexity, and enhance functional safety and diagnostics through harmonized control logic and optimized software architecture. The proposed approach involves a zonal architecture wherein a high-performance Domain Controller communicates via automotive-grade Ethernet and CAN-FD networks to each powertrain sub-system. The DC hosts a consolidated software stack incorporating AUTOSAR-compliant components, advanced scheduling techniques, and model-based control algorithms. Development and validation were performed using MATLAB/Simulink, PSIM, Vector tools, and HIL benches, with integration support via Adaptive AUTOSAR and middleware abstraction layers. In conclusion, the domain controller-based integrated powertrain architecture presents a scalable, modular, and production-ready solution that aligns with evolving EV platform strategies. It offers strategic business value through IP consolidation, reduced development cycles, modular software reuse, and simplified vehicle E/E architecture.