Solar flares are intense explosions occuring on the surface of the Sun. They emit radiation in the entire electromagnetic spectrum, up to the gamma-ray range. In particular, solar flares produce X-rays as a result of plasma heated to several million degrees and from accelerated electrons colliding with the dense layers of the solar surface. High-intensity solar flares often exhibit complex thermal structures that cannot be accurately described by a single isothermal approximation. Observations frequently reveal two distinct thermal components, a hot plasma (∼5–25 MK) and a super-hot plasma (>30 MK), both contributing simultaneously to the observed X-ray emission. The Spectrometer/Telescope for Imaging X-rays (STIX) is the instrument on board the ESA Solar Orbiter mission devoted to the observation of the X-ray emission in solar flares. The telescope applies an indirect imaging technique, and measures a limited number (∼30) of bi-dimensional Fourier components (or visibilities) of the flaring X-ray sources. Therefore, imaging the X-ray emission in solar flares from STIX visibilities is an inverse problem from limited Fourier data. In this talk, we will present a new technique that enables simultaneous imaging of hot and super-hot plasma in large solar flares using STIX observations. We will also demonstrate how the temperatures of the two thermal components can be estimated using group-lasso-type techniques. Finally, we will present the results of a study based on greedy approaches to determine which subset of the Fourier frequencies sampled by STIX is necessary for accurate reconstruction of the flaring X-ray sources.