Start by heating a medium heavy-bottomed pan over medium heat, adding the oil until shimmering.
Add the cumin and coriander seeds to the hot oil and toast gently for about 30 seconds until fragrant; they should crackle softly.
Stir in the diced onion and cook, stirring often, until golden and translucent—about 8 to 10 minutes. The onions should smell sweet and look tender.
Add the crushed garlic and grated ginger, cooking for another 30 seconds until fragrant and sizzling, filling the kitchen with warm, spicy aroma.
Pour in the coconut milk and stir well, bringing the mixture to a gentle simmer. Let it bubble softly for about 2 minutes until slightly thickened.
Add the green peas to the pan, stir to coat with the sauce, then cover and cook on low heat for 10-12 minutes until peas are tender but still vibrantly green.
Taste the curry and season with salt and chili flakes, adjusting to your spice preference. Let it simmer uncovered for another 2 minutes to meld flavors.
Remove from heat and squeeze fresh lemon juice over the curry, stirring to brighten the flavors and add a zesty finish.
Give the curry a final stir, then let it rest for a couple of minutes to allow flavors to settle. Serve hot with rice or flatbread, garnished with herbs if desired.