Tomato processing produces large quantities of by-products, mainly pomace, which are frequently discarded despite their significant nutritional and functional potential. The study aimed to evaluate the proximate analysis, volatiles, fatty acids, total antioxidant capacity, carotenoids, lycopene, and β-carotene in the pomace of three varieties of tomatoes (two Romanian cultivars and one Mediterranean cultivar) for potential valorization of these by-products. The mineral content in the tomato pomace was found to follow the order (average, mg kg⁻¹): K (13,090) > P (2793) > Ca (1121) > Mg (879) > Na (258) > Fe (12.3) > Zn (11.4) > Mn (7.0) > Cu (3.0). The fatty acid profiles revealed the presence of linoleic acid, oleic acid, and palmitic acids. All cultivars exhibited a high content of polyunsaturated fatty acid (PUFA) (55.7–62.3%) and a low content of omega-3 fatty acids (2%). Nutritional quality indices were calculated based on the fatty acid profiles. Analysis of volatile compounds revealed that Mediterranean cultivars were predominantly enriched in alcohols, hydrocarbons, and aldehydes, whereas Romanian cultivars had a high level of terpenes, along with hydrocarbons and aldehydes, contributing to their distinctive flavor profiles. The identified terpenes included β-phellandrene, terpinolene, limonene, ocimene, and cholestanone. All samples exhibited notable levels of bioactive compounds, particularly polyphenols and carotenoids. Additionally, high quantities of lycopene were found in the tomato by-products. The nutritional quality indices indicate that tomato pomace can be utilized as an ingredient to enhance the nutritional value of other products.