>> source: Plant-Based India by Dr Sheil Shukla, pg. 240

Heat the @olive oil{2%tsp} in a #wide pan or braising pan{} over medium heat. Add the @diced yellow onion{1} and @salt{1/2%tsp}, and cook, stirring occasionally, until softened and starting to brown, about 15 minutes. Adjust the heat between medium-low and medium to prevent the onions from browning too quickly.
 
Reduce the heat to medium-low. Add the @minced or crushed garlic{6%cloves} and @minced ginger{1.5%tsp} and continue to stir until lightly browned and fragrant, 3 to 5 minutes.

Add the @garam masala{1%tsp}, @coriander{1%tsp}, @cumin{1%tsp}, @red chili{1/2%tsp}, and @turmeric{1/2%tsp}, and stir for a few seconds to toast. Add the @tomato paste{1/3%cup} and @water{1%cup} and stir well to combine. Increase the heat to medium and cook, stirring occasionally, until thickened, about 10 minutes.

Transfer the onion and tomato mixture to a #blender, let it cool slightly, and blend until smooth. Store in an airtight container and refrigerate for a few days or freeze for up to 6 months.